File size: 94,427 Bytes
a1d2967
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
"""
embodied_pcei/src/ninja_env.py

High-performance physical simulation environment for the American Ninja Warrior course.
Built on MuJoCo with native Apple Silicon performance.

Features:
- Articulated bipedal humanoid with 21 joint torque actuators.
- Staged American Ninja Warrior course:
  * Stage 0: Flat sprint runway (0 to 8m)
  * Stage 1: Quad steps / angled stepping stones (8 to 18m)
  * Stage 2: Elevated balance beam (18 to 28m)
  * Stage 3: Hurdles & stepping barriers (28 to 38m)
  * Stage 4: Warped wall incline ramp & summit buzzer (38 to 48m)
- Raycast Pseudo-Vision: forward height probes measuring terrain/obstacle topology.
- Metabolic / Homeostatic Telemetry: lungs/stamina, stomach/hunger, heart/health.
- Built-in offscreen renderer for live web dashboard streaming.
"""

import numpy as np
import mujoco
from pathlib import Path
from typing import Dict, Tuple, Optional

XML_PATH = Path(__file__).resolve().parent.parent / "models" / "ninja_course.xml"
FLAT_ARENA_XML = Path(__file__).resolve().parent.parent / "models" / "flat_arena.xml"

# Obstacle Stage Milestones along +X
STAGE_MILESTONES = [
    (8.0,  "Stage 1: Quad Steps"),
    (18.0, "Stage 2: Balance Beam"),
    (28.0, "Stage 3: Hurdles"),
    (38.0, "Stage 4: Warped Wall"),
    (46.0, "Course Finish: Summit Buzzer"),
]

# 18 Progressive Navigation Waypoints across the 48m Ninja Warrior Course
# Format: (Target 3D Coordinate [X, Y, Z], Waypoint Label, Arrival Radius in meters)
COURSE_WAYPOINTS = [
    (np.array([3.0,  0.00, 1.33], dtype=np.float32), "Runway Accelerate 1",          1.2),
    (np.array([6.0,  0.00, 1.33], dtype=np.float32), "Runway Accelerate 2",          1.2),
    (np.array([8.0,  0.00, 1.33], dtype=np.float32), "Runway Exit Threshold",        1.0),
    (np.array([10.0, -0.60, 0.20], dtype=np.float32), "Stage 1: Quad Step 1 (Right)", 0.8),
    (np.array([12.2,  0.60, 0.30], dtype=np.float32), "Stage 1: Quad Step 2 (Left)",  0.8),
    (np.array([14.4, -0.50, 0.35], dtype=np.float32), "Stage 1: Quad Step 3 (Right)", 0.8),
    (np.array([16.6,  0.50, 0.40], dtype=np.float32), "Stage 1: Quad Step 4 (Left)",  0.8),
    (np.array([18.5,  0.00, 0.45], dtype=np.float32), "Platform Mid 1",               1.0),
    (np.array([20.5,  0.00, 0.50], dtype=np.float32), "Stage 2: Balance Beam Entry",  0.6),
    (np.array([23.5,  0.00, 0.50], dtype=np.float32), "Stage 2: Balance Beam Mid",    0.6),
    (np.array([26.5,  0.00, 0.50], dtype=np.float32), "Stage 2: Balance Beam Exit",   0.6),
    (np.array([28.5,  0.00, 0.50], dtype=np.float32), "Platform Mid 2",               1.0),
    (np.array([31.5,  0.00, 0.20], dtype=np.float32), "Stage 3: Hurdle 1",            0.9),
    (np.array([34.5,  0.00, 0.28], dtype=np.float32), "Stage 3: Hurdle 2",            0.9),
    (np.array([37.5,  0.00, 0.22], dtype=np.float32), "Stage 3: Hurdle 3",            0.9),
    (np.array([40.0,  0.00, 0.30], dtype=np.float32), "Stage 4: Warped Wall Approach",1.2),
    (np.array([42.5,  0.00, 0.70], dtype=np.float32), "Stage 4: Warped Wall Incline", 1.2),
    (np.array([47.5,  0.00, 2.45], dtype=np.float32), "Course Finish: Summit Buzzer", 0.6),
]

# Translucent Neon Color Palette for Multi-Agent Ghost Swarm Rendering
GHOST_PALETTE = [
    np.array([0.2, 0.7, 1.0, 0.16], dtype=np.float32),  # Neon Cyan
    np.array([0.7, 0.3, 1.0, 0.16], dtype=np.float32),  # Electric Purple
    np.array([0.1, 0.9, 0.6, 0.16], dtype=np.float32),  # Neon Emerald
    np.array([1.0, 0.55, 0.1, 0.16], dtype=np.float32), # Sunset Orange
    np.array([1.0, 0.2, 0.6, 0.16], dtype=np.float32),  # Neon Pink
    np.array([0.35, 0.8, 1.0, 0.16], dtype=np.float32), # Sky Blue
    np.array([0.85, 0.95, 0.2, 0.16], dtype=np.float32),# Lime Volt
]

# Canonical Reference Quiet Standing Equilibrium Pose (21 Actuated Joints)
# Torso at Z=1.168m, spine vertical, knees naturally flexed at 0.05 rad (~3 deg), arms down at sides
STAND_REF_QPOS = np.array([
    0.0, 0.0, 0.0,                      # abdomen_z, abdomen_y, abdomen_x
    0.0, 0.0, -0.05, 0.05, -0.025, 0.0, # right_hip_x, z, y, knee, ankle_y, ankle_x
    0.0, 0.0, -0.05, 0.05, -0.025, 0.0, # left_hip_x, z, y, knee, ankle_y, ankle_x
    0.65, 0.0, 0.0,                     # right_shoulder_x, y, elbow (down at side)
    -0.65, 0.0, 0.0,                    # left_shoulder_x, y, elbow (down at side)
], dtype=np.float32)

STAND_JOINT_WEIGHTS = np.array([
    1.5, 1.5, 1.5,                      # abdomen_z, abdomen_y, abdomen_x
    1.5, 1.5, 1.5, 1.5, 1.5, 1.5,       # right leg (hip_x, hip_z, hip_y, knee, ankle_y, ankle_x)
    1.5, 1.5, 1.5, 1.5, 1.5, 1.5,       # left leg (hip_x, hip_z, hip_y, knee, ankle_y, ankle_x)
    0.5, 0.5, 0.5,                      # right arm (shoulder_x, shoulder_y, elbow)
    0.5, 0.5, 0.5                       # left arm (shoulder_x, shoulder_y, elbow)
], dtype=np.float32)


class NinjaEnv:
    def __init__(self, xml_path: Optional[str] = None, frame_skip: int = 5, arena_mode: bool = True, stream_mode: str = "cruise"):
        self.arena_mode = arena_mode
        self.stream_mode = stream_mode  # "cruise", "stand", "getup", "reach"
        if xml_path is None:
            xml_path = str(FLAT_ARENA_XML if arena_mode else XML_PATH)
        self.model = mujoco.MjModel.from_xml_path(xml_path)
        self.data = mujoco.MjData(self.model)
        self.frame_skip = frame_skip
        
        self.dt = self.model.opt.timestep * frame_skip # 0.005 * 5 = 0.025s (40 Hz)
        
        self.n_actuators = self.model.nu # 21
        self.n_qpos = self.model.nq     # 28 (7 root + 21 joints)
        self.n_qvel = self.model.nv     # 27 (6 root + 21 joints)
        
        # Solid-State Angular LiDAR Sensor Configuration
        # 16 vertical beams (pitch: -35 deg to +15 deg) x 32 horizontal beams (yaw: -45 deg to +45 deg) = 512 rays
        self.num_lidar_v = 16
        self.num_lidar_h = 32
        self.num_lidar_rays = self.num_lidar_v * self.num_lidar_h # 512
        self.num_rays = self.num_lidar_rays # backwards-compatibility alias
        self.lidar_max_range = 10.0 # meters
        self.lidar_v_angles = np.radians(np.linspace(-35, 15, self.num_lidar_v))
        self.lidar_h_angles = np.radians(np.linspace(-45, 45, self.num_lidar_h))
        
        # Precompute unit direction vectors in head local coordinate frame
        # Forward = +X, Left = +Y, Up = +Z
        local_vectors = []
        for pitch in self.lidar_v_angles:
            for yaw in self.lidar_h_angles:
                vx = np.cos(pitch) * np.cos(yaw)
                vy = np.cos(pitch) * np.sin(yaw)
                vz = np.sin(pitch)
                v = np.array([vx, vy, vz], dtype=np.float64)
                v /= np.linalg.norm(v)
                local_vectors.append(v)
        self.lidar_local_vectors = np.array(local_vectors, dtype=np.float64) # (128, 3)
        self.current_lidar_grid = np.zeros((self.num_lidar_v, self.num_lidar_h), dtype=np.float32)
        self._geomid_buf = np.zeros(1, dtype=np.int32)
        self._visor_offset = np.array([0.15, 0.0, 0.0], dtype=np.float64)
        
        # Metabolic internal states
        self.stamina = 1.0 # 0.0 to 1.0
        self.health = 1.0  # 0.0 to 1.0
        self.hunger = 0.0  # 0.0 to 1.0
        
        # Milestone tracking & Course Waypoints
        self.milestones_reached = set()
        self.waypoints_reached = set()
        self.current_wp_idx = 0
        self.furthest_x = 0.0
        self.max_steps = 1000

        # Flat Arena & Dynamic Random Goal Navigation State (Stream 4: Cruise)
        self.goal_pos = np.array([5.0, 0.0, 1.25], dtype=np.float32)
        self.goals_completed = 0
        self.goal_arrival_radius = 2.0      # Wide capture radius (2.0m): easily clears by walking near target
        self.min_dist_to_goal = 5.0
        self.prev_dist_to_goal = 5.0
        self.steps_not_approaching = 0
        self.transition_leeway_window = 90  # ~2.25s leeway (90 steps at 40Hz) for turning & realignment
        self.goal_transition_steps = 0      # No leeway on initial spawn (must advance immediately)

        # Stream 1: Quiet Standing Stillness State
        self.stand_still_steps = 0
        self.stand_drift_steps = 0
        self.stand_one_leg_steps = 0

        # Stream 2: Fall Recovery State (Ragdoll & Curated Library)
        self.fall_state_type = "random_ragdoll"
        self.consecutive_upright_steps = 0
        self.prev_z = 0.20
        self.prev_head_z = 0.20
        self.getup_stagnant_steps = 0
        self.max_elevation_achieved = 0.20
        self.max_head_elevation = 0.20
        self.getup_goal_pos = np.array([0.0, 0.0, 1.168], dtype=np.float32)
        self.getup_success_count = 0

        # Stream 3: Bilateral Hand Reaching State (Bolted Torso)
        self.active_reach_hand = "right"
        self.reach_target_pos = np.array([0.35, -0.25, 1.35], dtype=np.float32)
        self.reach_touches = 0
        self.prev_reach_dist = 0.40
        self.min_reach_dist = 0.40
        self.steps_on_reach_target = 0
        self.steps_receding_reach = 0
        
        # Bilateral gait stance duty-cycle counters
        self.r_foot_contact_steps = 0
        self.l_foot_contact_steps = 0
        
        # Offscreen renderer instance (lazy-loaded)
        self._renderer = None
        
        # Cache body and geom IDs for fast lookups
        self.torso_body_id = mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_BODY, "torso")
        self.head_body_id = mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_BODY, "head")
        self.r_foot_id = mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_BODY, "right_foot")
        self.l_foot_id = mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_BODY, "left_foot")
        self.r_foot_geom_id = mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_GEOM, "right_foot_geom")
        self.l_foot_geom_id = mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_GEOM, "left_foot_geom")
        self.r_hand_geom_id = mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_GEOM, "right_hand")
        self.l_hand_geom_id = mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_GEOM, "left_hand")
        self.r_arm_body_id = mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_BODY, "right_lower_arm")
        self.l_arm_body_id = mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_BODY, "left_lower_arm")

        # Cache leg joint qpos indices for athletic stance and gait monitoring
        self.r_knee_qpos = self.model.jnt_qposadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "right_knee")]
        self.l_knee_qpos = self.model.jnt_qposadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "left_knee")]
        self.r_hip_qpos = self.model.jnt_qposadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "right_hip_y")]
        self.l_hip_qpos = self.model.jnt_qposadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "left_hip_y")]
        self.r_ankle_qpos = self.model.jnt_qposadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "right_ankle_y")]
        self.l_ankle_qpos = self.model.jnt_qposadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "left_ankle_y")]
        # Cache abdomen joint qpos indices for core posture alignment
        self.abdomen_x_qpos = self.model.jnt_qposadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "abdomen_x")]
        self.abdomen_y_qpos = self.model.jnt_qposadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "abdomen_y")]
        self.abdomen_z_qpos = self.model.jnt_qposadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "abdomen_z")]

        # Cache arm joint qpos and dof velocity indices for bilateral reach
        self.arm_qpos_indices = [
            self.model.jnt_qposadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "right_shoulder_x")],
            self.model.jnt_qposadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "right_shoulder_y")],
            self.model.jnt_qposadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "right_elbow")],
            self.model.jnt_qposadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "left_shoulder_x")],
            self.model.jnt_qposadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "left_shoulder_y")],
            self.model.jnt_qposadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "left_elbow")],
        ]
        self.arm_dof_indices = [
            self.model.jnt_dofadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "right_shoulder_x")],
            self.model.jnt_dofadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "right_shoulder_y")],
            self.model.jnt_dofadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "right_elbow")],
            self.model.jnt_dofadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "left_shoulder_x")],
            self.model.jnt_dofadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "left_shoulder_y")],
            self.model.jnt_dofadr[mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_JOINT, "left_elbow")],
        ]

        # Cache collision geoms for physical impact detection (head, visor, chest, torso)
        # All geoms belonging to world body (body 0) are environmental surfaces: floor + all obstacles
        self.world_obstacle_geoms = {i for i in range(self.model.ngeom) if self.model.geom_bodyid[i] == 0}
        self.body_impact_geoms = {
            mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_GEOM, "torso_geom"),
            mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_GEOM, "chest_geom"),
            mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_GEOM, "head_geom"),
            mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_GEOM, "visor"),
        }

        # Cache humanoid geom indices (all geoms belonging to non-world bodies) for ghost rendering
        self.humanoid_geoms = [i for i in range(self.model.ngeom) if self.model.geom_bodyid[i] != 0]

        # Cache limb geoms for Get-Up multi-phase floor contact righting
        self.r_shin_geom_id = mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_GEOM, "right_shin_geom")
        self.l_shin_geom_id = mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_GEOM, "left_shin_geom")
        self.support_hand_geoms = {
            self.r_hand_geom_id,
            self.l_hand_geom_id,
            mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_GEOM, "right_larm_geom"),
            mujoco.mj_name2id(self.model, mujoco.mjtObj.mjOBJ_GEOM, "left_larm_geom"),
        }
        self.support_knee_geoms = {self.r_shin_geom_id, self.l_shin_geom_id}

    def _lock_torso_for_reach(self):
        """Bolts root torso, core spine, and legs in neutral athletic stance (Stream 3: Isolated Arm Motor Cortex)."""
        self.data.qpos[0] = 0.0
        self.data.qpos[1] = 0.0
        self.data.qpos[2] = 1.35
        self.data.qpos[3:7] = np.array([1.0, 0.0, 0.0, 0.0])  # Upright quaternion
        self.data.qvel[0:6] = 0.0  # Zero base linear & angular velocity
        # Lock core spine neutral
        self.data.qpos[7:10] = 0.0  # abdomen_z, abdomen_y, abdomen_x
        # Lock legs in neutral supportive stance
        self.data.qpos[10:22] = 0.0 # zero all hip, knee, ankle
        self.data.qpos[self.r_knee_qpos] = 0.30
        self.data.qpos[self.l_knee_qpos] = 0.30
        self.data.qpos[self.r_ankle_qpos] = -0.10
        self.data.qpos[self.l_ankle_qpos] = -0.10
        self.data.qvel[6:21] = 0.0  # Zero core & lower body velocities (DOFs 6 to 20, preserving arm DOFs 21:27)

    def _sample_reach_target(self):
        """
        Samples a randomized 3D reach goal via Forward Kinematics (FK) from the active arm's
        reachable joint space, mathematically guaranteeing 100.0% of targets are physically reachable (Stream 3).
        """
        self.active_reach_hand = np.random.choice(["right", "left"])
        
        # Save current posture
        saved_qpos = self.data.qpos.copy()
        target_pos = None

        # Sample joint angles from the arm's valid forward/lateral reachable envelope
        for _ in range(25):
            if self.active_reach_hand == "right":
                # Right arm envelope: shoulder roll/pitch and elbow flexion
                target_sx = float(np.random.uniform(-0.75, 0.40))
                target_sy = float(np.random.uniform(-0.60, 0.85))
                target_el = float(np.random.uniform(-1.10, 0.45))
                self.data.qpos[self.arm_qpos_indices[0]] = target_sx  # right_shoulder_x
                self.data.qpos[self.arm_qpos_indices[1]] = target_sy  # right_shoulder_y
                self.data.qpos[self.arm_qpos_indices[2]] = target_el  # right_elbow
                mujoco.mj_forward(self.model, self.data)
                cand_pos = self.data.geom_xpos[self.r_hand_geom_id].copy()
            else:
                # Left arm envelope: shoulder roll/pitch and elbow flexion
                target_sx = float(np.random.uniform(-0.40, 0.75))
                target_sy = float(np.random.uniform(-0.60, 0.85))
                target_el = float(np.random.uniform(-0.45, 1.10))
                self.data.qpos[self.arm_qpos_indices[3]] = target_sx  # left_shoulder_x
                self.data.qpos[self.arm_qpos_indices[4]] = target_sy  # left_shoulder_y
                self.data.qpos[self.arm_qpos_indices[5]] = target_el  # left_elbow
                mujoco.mj_forward(self.model, self.data)
                cand_pos = self.data.geom_xpos[self.l_hand_geom_id].copy()

            # Restore original pose to measure distance
            self.data.qpos[:] = saved_qpos
            mujoco.mj_forward(self.model, self.data)
            curr_h = self.data.geom_xpos[self.r_hand_geom_id] if self.active_reach_hand == "right" else self.data.geom_xpos[self.l_hand_geom_id]
            dist_to_cand = float(np.linalg.norm(curr_h - cand_pos))
            target_pos = cand_pos
            # Ensure target is at least 0.16m away so the agent must actively articulate its arm
            if dist_to_cand >= 0.16:
                break

        # Always restore state cleanly
        self.data.qpos[:] = saved_qpos
        mujoco.mj_forward(self.model, self.data)

        self.reach_target_pos = target_pos.astype(np.float32)
        self.goal_pos = self.reach_target_pos.copy()

    def _apply_fall_state(self, pose_name: Optional[str] = None):
        """
        Initializes agent in a randomized fall state with 360Β° randomized yaw,
        perturbed joints, physics contact settling, and a randomized standing destination goal (Stream 2).
        """
        if pose_name is None:
            poses = ["prone", "supine", "lateral_left", "lateral_right", "kneeling_crumpled", "seated_slumped", "random_ragdoll"]
            pose_name = np.random.choice(poses)
        self.fall_state_type = pose_name

        self.data.qvel[:] = 0.0
        # Random initial floor translation offset
        spawn_x = float(np.random.uniform(-0.4, 0.4))
        spawn_y = float(np.random.uniform(-0.4, 0.4))

        # Base orientation quaternion [w, x, y, z] per canonical pose
        if pose_name == "prone":
            # Lying on stomach: pitch 90 deg forward
            self.data.qpos[0:3] = np.array([spawn_x, spawn_y, 0.22])
            q_base = np.array([0.7071, 0.0, 0.7071, 0.0])
            self.data.qpos[self.r_knee_qpos] = 0.2
            self.data.qpos[self.l_knee_qpos] = 0.2
        elif pose_name == "supine":
            # Lying on back: pitch 90 deg backward
            self.data.qpos[0:3] = np.array([spawn_x, spawn_y, 0.22])
            q_base = np.array([0.7071, 0.0, -0.7071, 0.0])
            self.data.qpos[self.r_knee_qpos] = 0.3
            self.data.qpos[self.l_knee_qpos] = 0.3
        elif pose_name == "lateral_left":
            # Lying on left flank: roll 90 deg left
            self.data.qpos[0:3] = np.array([spawn_x, spawn_y, 0.22])
            q_base = np.array([0.7071, -0.7071, 0.0, 0.0])
        elif pose_name == "lateral_right":
            # Lying on right flank: roll 90 deg right
            self.data.qpos[0:3] = np.array([spawn_x, spawn_y, 0.22])
            q_base = np.array([0.7071, 0.7071, 0.0, 0.0])
        elif pose_name == "kneeling_crumpled":
            # Crumpled on knees, torso pitched forward
            self.data.qpos[0:3] = np.array([spawn_x, spawn_y, 0.48])
            q_base = np.array([0.9238, 0.0, 0.3826, 0.0])
            self.data.qpos[self.r_knee_qpos] = 1.7
            self.data.qpos[self.l_knee_qpos] = 1.7
            self.data.qpos[self.r_hip_qpos] = -1.0
            self.data.qpos[self.l_hip_qpos] = -1.0
        elif pose_name == "seated_slumped":
            # Slumped seated on buttocks, legs forward
            self.data.qpos[0:3] = np.array([spawn_x, spawn_y, 0.35])
            q_base = np.array([0.9238, 0.0, -0.3826, 0.0])
            self.data.qpos[self.r_hip_qpos] = -1.4
            self.data.qpos[self.l_hip_qpos] = -1.4
            self.data.qpos[self.r_knee_qpos] = 0.2
            self.data.qpos[self.l_knee_qpos] = 0.2
        else:
            # Random ragdoll drop: drop from 0.45m with completely randomized 3D orientation
            self.data.qpos[0:3] = np.array([spawn_x, spawn_y, float(np.random.uniform(0.40, 0.60))])
            rand_quat = np.random.uniform(-1.0, 1.0, size=4)
            q_base = rand_quat / np.linalg.norm(rand_quat)

        # Apply randomized 360Β° yaw rotation to base pose quaternion
        yaw = float(np.random.uniform(-np.pi, np.pi))
        q_yaw = np.array([np.cos(yaw / 2.0), 0.0, 0.0, np.sin(yaw / 2.0)], dtype=np.float64)
        # Quaternion multiplication: q_yaw * q_base
        w1, x1, y1, z1 = q_yaw
        w2, x2, y2, z2 = q_base
        q_rot = np.array([
            w1*w2 - x1*x2 - y1*y2 - z1*z2,
            w1*x2 + x1*w2 + y1*z2 - z1*y2,
            w1*y2 - x1*z2 + y1*w2 + z1*x2,
            w1*z2 + x1*y2 - y1*x2 + z1*w2,
        ], dtype=np.float64)
        self.data.qpos[3:7] = q_rot / np.linalg.norm(q_rot)

        # Stochastic joint perturbation across all 21 joint degrees of freedom
        self.data.qpos[7:] += np.random.uniform(-0.20, 0.20, size=self.n_actuators)

        # Settle contact forces smoothly (12 passive sub-steps with zero actuation)
        mujoco.mj_forward(self.model, self.data)
        for _ in range(12):
            self.data.ctrl[:] = 0.0
            mujoco.mj_step(self.model, self.data)
        self.data.qvel[:] = 0.0
        mujoco.mj_forward(self.model, self.data)

        # Sample a randomized standing destination goal beacon (0.6m - 1.8m away at random heading)
        stand_dist = float(np.random.uniform(0.6, 1.8))
        stand_heading = float(np.random.uniform(-np.pi, np.pi))
        cur_torso = self.data.xpos[self.torso_body_id]
        gx = float(cur_torso[0] + stand_dist * np.cos(stand_heading))
        gy = float(cur_torso[1] + stand_dist * np.sin(stand_heading))
        gz = 1.168  # Grounded standing torso height equilibrium
        self.getup_goal_pos = np.array([gx, gy, gz], dtype=np.float32)
        self.goal_pos = self.getup_goal_pos.copy()

    def _sample_new_goal(self, is_initial: bool = False):
        """Samples a new random navigation target within the 50m x 50m flat arena."""
        torso_pos = self.data.xpos[self.torso_body_id]
        if is_initial:
            # Initial target: distance 5.0m - 7.5m in forward cone (-60 deg to +60 deg)
            dist = float(np.random.uniform(5.0, 7.5))
            angle = float(np.random.uniform(-np.pi / 3, np.pi / 3))
            self.goal_transition_steps = 0  # Spawn directly facing target: immediate approach required
        else:
            # Subsequent target: distance 5.5m - 9.0m in full 360 deg omnidirectional bearing
            dist = float(np.random.uniform(5.5, 9.0))
            angle = float(np.random.uniform(-np.pi, np.pi))
            self.goal_transition_steps = self.transition_leeway_window  # ~1.85s direction change leeway
            
        gx = float(np.clip(torso_pos[0] + dist * np.cos(angle), -22.0, 22.0))
        gy = float(np.clip(torso_pos[1] + dist * np.sin(angle), -22.0, 22.0))

        # Ensure newly sampled target is at least (arrival_radius + 1.5m = 3.5m) away from current torso
        for _ in range(20):
            if np.linalg.norm(np.array([gx - torso_pos[0], gy - torso_pos[1]])) >= (self.goal_arrival_radius + 1.5):
                break
            center_angle = float(np.arctan2(-torso_pos[1], -torso_pos[0]))
            angle = float(center_angle + np.random.uniform(-np.pi / 4, np.pi / 4))
            dist = float(np.random.uniform(5.5, 8.5))
            gx = float(np.clip(torso_pos[0] + dist * np.cos(angle), -22.0, 22.0))
            gy = float(np.clip(torso_pos[1] + dist * np.sin(angle), -22.0, 22.0))

        gz = 1.25  # Torso/chest level
        self.goal_pos = np.array([gx, gy, gz], dtype=np.float32)
        self.min_dist_to_goal = float(np.linalg.norm(self.goal_pos - torso_pos))
        self.prev_dist_to_goal = float(self.min_dist_to_goal)
        self.steps_since_progress = 0
        self.steps_not_approaching = 0
        self.negative_vx_steps = 0

    @property
    def observation_dim(self) -> int:
        """
        Total observation vector length:
        - Torso height z: 1
        - Torso orientation (forward & up vectors): 6
        - Torso linear velocity (local/global): 3
        - Torso angular velocity: 3
        - 21 joint angles: 21
        - 21 joint velocities: 21
        - 2 foot contact forces: 2
        - 512 solid-state LiDAR range rays (16x32 grid): 512
        - 3 ego-centric relative waypoint vector (Ξ”x, Ξ”y, Ξ”z local): 3
        - 3 metabolic stats (stamina, health, hunger): 3
        Total: 1 + 6 + 3 + 3 + 21 + 21 + 2 + 512 + 3 + 3 = 575
        """
        return 575

    @property
    def action_dim(self) -> int:
        return self.n_actuators # 21

    def reset(self, seed: Optional[int] = None, spawn_x: float = 0.0, initial_vx: float = 0.0) -> np.ndarray:
        if seed is not None:
            np.random.seed(seed)
            
        mujoco.mj_resetData(self.model, self.data)
        
        # Initial root pose: at X=spawn_x, Y=0, Z=1.33 (athletic bent-knee stance)
        self.data.qpos[0] = spawn_x   # X
        self.data.qpos[1] = 0.0       # Y
        self.data.qpos[2] = 1.33      # Z
        self.data.qpos[3:7] = np.array([1.0, 0.0, 0.0, 0.0]) # Quaternion (unit)
        
        # Staggered lead leg initialization: alternates 50% left lead, 50% right lead
        # This breaks single-leg asymmetric gait traps and forces both thighs to cycle
        lead_leg = np.random.choice(["right", "left"])
        if lead_leg == "right":
            self.data.qpos[self.r_hip_qpos] = -0.35  # Right thigh poised forward
            self.data.qpos[self.r_knee_qpos] = 0.45
            self.data.qpos[self.r_ankle_qpos] = -0.15
            self.data.qpos[self.l_hip_qpos] = 0.05   # Left leg supporting in stance
            self.data.qpos[self.l_knee_qpos] = 0.25
            self.data.qpos[self.l_ankle_qpos] = -0.05
        else:
            self.data.qpos[self.l_hip_qpos] = -0.35  # Left thigh poised forward
            self.data.qpos[self.l_knee_qpos] = 0.45
            self.data.qpos[self.l_ankle_qpos] = -0.15
            self.data.qpos[self.r_hip_qpos] = 0.05   # Right leg supporting in stance
            self.data.qpos[self.r_knee_qpos] = 0.25
            self.data.qpos[self.r_ankle_qpos] = -0.05
        
        # Add slight stochastic noise to joint angles for exploration diversity
        joint_noise = np.random.uniform(-0.03, 0.03, size=self.n_actuators)
        self.data.qpos[7:] += joint_noise
        
        # Zero velocities with tiny noise (or inject forward running momentum if pioneer spawn)
        self.data.qvel[:] = np.random.uniform(-0.02, 0.02, size=self.n_qvel)
        if initial_vx > 0.0:
            self.data.qvel[0] = initial_vx + np.random.uniform(-0.1, 0.1)
        
        # Reset internal stats
        self.stamina = 1.0
        self.health = 1.0
        self.hunger = 0.0
        
        self.milestones_reached = set()
        self.waypoints_reached = set()
        self.current_wp_idx = 0

        if self.stream_mode == "stand":
            # Stream 1: Quiet Standing Balance (Canonical Reference Equilibrium Stance)
            self.data.qpos[0] = 0.0
            self.data.qpos[1] = 0.0
            self.data.qpos[2] = 1.168
            self.data.qpos[3:7] = np.array([1.0, 0.0, 0.0, 0.0])
            self.data.qvel[:] = 0.0
            self.data.qpos[7:7 + self.n_actuators] = STAND_REF_QPOS.copy()
            # Add slight stochastic exploration noise (+/- 0.015 rad ~ 0.8 deg) so agent learns to balance
            self.data.qpos[7:7 + self.n_actuators] += np.random.uniform(-0.015, 0.015, size=self.n_actuators)
            # Settle foot ground contacts smoothly (10 passive sub-steps with zero actuation)
            mujoco.mj_forward(self.model, self.data)
            for _ in range(10):
                self.data.ctrl[:] = 0.0
                mujoco.mj_step(self.model, self.data)
            self.data.qvel[:] = 0.0
            mujoco.mj_forward(self.model, self.data)
            self.goal_pos = np.array([0.0, 0.0, 1.168], dtype=np.float32)
            self.stand_still_steps = 0
            self.stand_drift_steps = 0
            self.stand_one_leg_steps = 0
            self.goals_completed = 0
        elif self.stream_mode == "getup":
            # Stream 2: Fall Recovery (Randomized 360Β° poses & standing destination goal)
            self._apply_fall_state()
            self.prev_z = float(self.data.xpos[self.torso_body_id][2])
            self.prev_head_z = float(self.data.xpos[self.head_body_id][2])
            self.consecutive_upright_steps = 0
            self.getup_stagnant_steps = 0
            self.max_elevation_achieved = self.prev_z
            self.max_head_elevation = self.prev_head_z
            self.getup_success_count = 0
            self.goals_completed = 0
        elif self.stream_mode == "reach":
            # Stream 2: Bilateral Hand Reaching (Bolted Torso with neutral resting arm configuration)
            self._lock_torso_for_reach()
            # Initialize both arms down at sides (natural resting posture at hip)
            self.data.qpos[self.arm_qpos_indices[0]] = 0.65 + float(np.random.uniform(-0.03, 0.03))  # right_shoulder_x (down at side)
            self.data.qpos[self.arm_qpos_indices[1]] = float(np.random.uniform(-0.03, 0.03))         # right_shoulder_y
            self.data.qpos[self.arm_qpos_indices[2]] = float(np.random.uniform(-0.03, 0.03))         # right_elbow
            self.data.qpos[self.arm_qpos_indices[3]] = -0.65 + float(np.random.uniform(-0.03, 0.03)) # left_shoulder_x (down at side)
            self.data.qpos[self.arm_qpos_indices[4]] = float(np.random.uniform(-0.03, 0.03))         # left_shoulder_y
            self.data.qpos[self.arm_qpos_indices[5]] = float(np.random.uniform(-0.03, 0.03))         # left_elbow
            self.data.qvel[self.arm_dof_indices] = 0.0
            mujoco.mj_forward(self.model, self.data)
            self._sample_reach_target()
            is_right_target = (self.active_reach_hand == "right")
            active_h = self.data.geom_xpos[self.r_hand_geom_id] if is_right_target else self.data.geom_xpos[self.l_hand_geom_id]
            self.prev_reach_dist = float(np.linalg.norm(active_h - self.reach_target_pos))
            self.min_reach_dist = self.prev_reach_dist
            self.reach_touches = 0
            self.steps_on_reach_target = 0
            self.steps_receding_reach = 0
            self.goals_completed = 0
        elif self.arena_mode:
            self.goals_completed = 0
            self._sample_new_goal(is_initial=True)
        else:
            # Fast-forward waypoint index if spawning downfield
            for idx, (wp_pos, _, _) in enumerate(COURSE_WAYPOINTS):
                if wp_pos[0] > spawn_x + 0.3:
                    self.current_wp_idx = idx
                    break
                
        self.spawn_x = float(spawn_x)
        self.furthest_x = float(spawn_x)
        self.current_step = 0
        self.steps_since_progress = 0
        self.last_progress_x = float(spawn_x)
        self.negative_vx_steps = 0
        self.steps_not_approaching = 0
        self.r_foot_contact_steps = 0
        self.l_foot_contact_steps = 0
        
        mujoco.mj_forward(self.model, self.data)
        return self._get_obs()

    def _get_obs(self) -> np.ndarray:
        # 1. Torso state
        torso_xpos = self.data.xpos[self.torso_body_id] # (3,)
        torso_xmat = self.data.xmat[self.torso_body_id].reshape(3, 3) # (3, 3)
        forward_vec = torso_xmat[:, 0] # Local X axis in world frame
        up_vec = torso_xmat[:, 2]      # Local Z axis in world frame
        
        torso_cvel = self.data.cvel[self.torso_body_id] # 6D: [ang_vel(3), lin_vel(3)]
        ang_vel = torso_cvel[:3]
        lin_vel = torso_cvel[3:]
        
        # 2. Joint states (21 angles, 21 velocities)
        joint_qpos = self.data.qpos[7:7 + self.n_actuators]
        joint_qvel = self.data.qvel[6:6 + self.n_actuators]
        
        # 3. Touch sensors & Task-Specific Contact Indicators
        touch_forces = np.zeros(2, dtype=np.float32)
        if self.stream_mode == "reach":
            # For isolated Reach, legs are bolted stationary. Repurpose touch_forces as explicit Active Hand Indicator:
            # [1.0, 0.0] -> Right Hand Active | [0.0, 1.0] -> Left Hand Active
            if self.active_reach_hand == "right":
                touch_forces[0] = 1.0
                touch_forces[1] = 0.0
            else:
                touch_forces[0] = 0.0
                touch_forces[1] = 1.0
        else:
            if self.model.nsensor >= 2:
                touch_forces[0] = np.clip(self.data.sensordata[0] / 100.0, 0.0, 5.0) # Right foot
                touch_forces[1] = np.clip(self.data.sensordata[1] / 100.0, 0.0, 5.0) # Left foot
            
        # 4. True Solid-State Angular LiDAR (512 rays from visor/eyes)
        lidar_obs = self._compute_lidar_vision()
        
        # 5. Dynamic Goal / Progressive Waypoint (Ego-centric local relative vector)
        if self.stream_mode == "stand":
            rel_world = self.goal_pos - torso_xpos
            rel_local = torso_xmat.T @ rel_world
            waypoint_obs = np.array([
                np.clip(rel_local[0] / 10.0, -1.0, 1.0),
                np.clip(rel_local[1] / 5.0, -1.0, 1.0),
                np.clip(rel_local[2] / 2.0, -1.0, 1.0),
            ], dtype=np.float32)
        elif self.stream_mode == "getup":
            rel_world = self.getup_goal_pos - torso_xpos
            rel_local = torso_xmat.T @ rel_world
            waypoint_obs = np.array([
                np.clip(rel_local[0] / 5.0, -1.0, 1.0),
                np.clip(rel_local[1] / 5.0, -1.0, 1.0),
                np.clip(rel_local[2] / 2.0, -1.0, 1.0),
            ], dtype=np.float32)
        elif self.stream_mode == "reach":
            # Direct closed-loop motor servoing: vector from ACTIVE HAND directly to the reach target orb!
            active_h = self.data.geom_xpos[self.r_hand_geom_id] if (self.active_reach_hand == "right") else self.data.geom_xpos[self.l_hand_geom_id]
            rel_hand_world = self.reach_target_pos - active_h
            rel_hand_local = torso_xmat.T @ rel_hand_world
            waypoint_obs = np.array([
                np.clip(rel_hand_local[0] / 0.6, -1.0, 1.0),
                np.clip(rel_hand_local[1] / 0.6, -1.0, 1.0),
                np.clip(rel_hand_local[2] / 0.6, -1.0, 1.0),
            ], dtype=np.float32)
        elif self.arena_mode:
            target_pos = self.goal_pos
            rel_world = target_pos - torso_xpos
            rel_local = torso_xmat.T @ rel_world
            waypoint_obs = np.array([
                np.clip(rel_local[0] / 10.0, -1.0, 1.0),
                np.clip(rel_local[1] / 5.0, -1.0, 1.0),
                np.clip(rel_local[2] / 2.0, -1.0, 1.0),
            ], dtype=np.float32)
        else:
            target_pos = COURSE_WAYPOINTS[self.current_wp_idx][0]
            rel_world = target_pos - torso_xpos
            rel_local = torso_xmat.T @ rel_world
            waypoint_obs = np.array([
                np.clip(rel_local[0] / 10.0, -1.0, 1.0),
                np.clip(rel_local[1] / 5.0, -1.0, 1.0),
                np.clip(rel_local[2] / 2.0, -1.0, 1.0),
            ], dtype=np.float32)

        # 6. Metabolic state (stamina, health, hunger/task-channel)
        if self.stream_mode == "reach":
            hand_indicator = 1.0 if (self.active_reach_hand == "right") else -1.0
            metabolic_obs = np.array([self.stamina, self.health, hand_indicator], dtype=np.float32)
        else:
            metabolic_obs = np.array([self.stamina, self.health, self.hunger], dtype=np.float32)
        
        obs = np.concatenate([
            np.array([torso_xpos[2]], dtype=np.float32), # Torso Z (1)
            forward_vec.astype(np.float32),              # 3
            up_vec.astype(np.float32),                   # 3
            lin_vel.astype(np.float32),                  # 3
            ang_vel.astype(np.float32),                  # 3
            joint_qpos.astype(np.float32),               # 21
            joint_qvel.astype(np.float32),               # 21
            touch_forces,                                # 2
            lidar_obs,                                   # 512
            waypoint_obs,                                # 3
            metabolic_obs,                               # 3
        ])
        
        return np.nan_to_num(obs, nan=0.0, posinf=50.0, neginf=-50.0)

    def _compute_lidar_vision(self) -> np.ndarray:
        """
        True Solid-State Angular LiDAR scan from the robot's visor/eyes.
        Casts 128 rays (8 vertical elevation x 16 horizontal azimuth) using MuJoCo's native C raycaster.
        Returns normalized range vector (128,) in [0.0, 1.0].
        """
        head_pos = self.data.xpos[self.head_body_id]
        head_mat = self.data.xmat[self.head_body_id].reshape(3, 3)
        
        # Ray origin: 0.15m forward from head center through visor
        ray_origin = np.ascontiguousarray(head_pos + head_mat @ self._visor_offset, dtype=np.float64)
        
        # Transform all 128 precomputed local vectors to world coordinates
        # (128, 3) @ (3, 3).T -> (128, 3)
        world_vectors = self.lidar_local_vectors @ head_mat.T
        
        normalized_ranges = np.zeros(self.num_lidar_rays, dtype=np.float32)
        raw_grid = np.zeros((self.num_lidar_v, self.num_lidar_h), dtype=np.float32)
        
        ray_idx = 0
        for row in range(self.num_lidar_v):
            for col in range(self.num_lidar_h):
                vec = np.ascontiguousarray(world_vectors[ray_idx], dtype=np.float64)
                dist = mujoco.mj_ray(self.model, self.data, ray_origin, vec, None, 1, -1, self._geomid_buf)
                
                if dist >= 0:
                    gid = int(self._geomid_buf[0])
                    if gid in self.humanoid_geoms:
                        actual_dist = self.lidar_max_range
                    else:
                        actual_dist = min(dist, self.lidar_max_range)
                else:
                    actual_dist = self.lidar_max_range
                    
                raw_grid[row, col] = actual_dist
                # Zero-centered range: -0.5 (impact / 0m) to +0.5 (clear / 10m), eliminates DC bias
                normalized_ranges[ray_idx] = (actual_dist / self.lidar_max_range) - 0.5
                ray_idx += 1
                
        self.current_lidar_grid = raw_grid
        return normalized_ranges

    def _compute_pseudo_vision(self, agent_x: float, agent_y: float, agent_z: float) -> np.ndarray:
        """Backwards compatibility fallback for 1D pseudo-vision."""
        return self._compute_lidar_vision()[:16]

    def step(self, action: np.ndarray) -> Tuple[np.ndarray, float, bool, bool, Dict]:
        self.current_step += 1
        
        # Clip action to [-1.0, 1.0]
        action = np.clip(action, -1.0, 1.0)
        self.data.ctrl[:] = action
        if self.stream_mode == "reach":
            # For isolated arm reaching, freeze motor commands to core and legs
            self.data.ctrl[0:15] = 0.0

        # Substep physics
        for _ in range(self.frame_skip):
            mujoco.mj_step(self.model, self.data)
            if self.stream_mode == "reach":
                self._lock_torso_for_reach()
            
        # Extract state measurements
        torso_xpos = self.data.xpos[self.torso_body_id]
        x, y, z = torso_xpos[0], torso_xpos[1], torso_xpos[2]
        
        torso_cvel = self.data.cvel[self.torso_body_id]
        vx = torso_cvel[3] # Forward linear velocity
        vy = torso_cvel[4]
        
        torso_xmat = self.data.xmat[self.torso_body_id].reshape(3, 3)
        up_z = torso_xmat[2, 2] # Cosine of torso vertical tilt
        
        # Update metabolic stats
        torque_cost = np.sum(np.square(action))
        self.stamina = np.clip(self.stamina - (torque_cost * 0.0003) + 0.0005, 0.0, 1.0)
        self.hunger = np.clip(self.hunger + 0.0001, 0.0, 1.0)
        
        # Multi-limb ground contact detection for floor righting and locomotion
        contact_r = False
        contact_l = False
        contact_hand = False
        contact_knee = False
        for c_idx in range(self.data.ncon):
            c = self.data.contact[c_idx]
            g1, g2 = c.geom1, c.geom2
            if (g1 == self.r_foot_geom_id and g2 in self.world_obstacle_geoms) or (g2 == self.r_foot_geom_id and g1 in self.world_obstacle_geoms):
                contact_r = True
            if (g1 == self.l_foot_geom_id and g2 in self.world_obstacle_geoms) or (g2 == self.l_foot_geom_id and g1 in self.world_obstacle_geoms):
                contact_l = True
            if (g1 in self.support_hand_geoms and g2 in self.world_obstacle_geoms) or (g2 in self.support_hand_geoms and g1 in self.world_obstacle_geoms):
                contact_hand = True
            if (g1 in self.support_knee_geoms and g2 in self.world_obstacle_geoms) or (g2 in self.support_knee_geoms and g1 in self.world_obstacle_geoms):
                contact_knee = True

        touch_r = contact_r or (bool(self.data.sensordata[0] > 5.0) if self.model.nsensor >= 1 else False)
        touch_l = contact_l or (bool(self.data.sensordata[1] > 5.0) if self.model.nsensor >= 2 else False)
        if touch_r:
            self.r_foot_contact_steps += 1
        if touch_l:
            self.l_foot_contact_steps += 1

        upright_scale = float(np.clip((z - 0.45) / 0.40, 0.0, 1.0)) # 0 at z<=0.45m, 1.0 at z>=0.85m
        in_leeway = False
        torso_speed = float(np.linalg.norm(torso_cvel[3:]))

        # ── STREAM 1: QUIET STANDING STILLNESS (REFERENCE POSE SIMILARITY) ────────
        if self.stream_mode == "stand":
            head_z = float(self.data.xpos[self.head_body_id][2])
            dist_from_origin = float(np.linalg.norm([x, y]))
            
            # 1. Joint Configuration Similarity:
            # Gaussian kernel comparing 21 actuated joints against canonical STAND_REF_QPOS
            current_qpos = self.data.qpos[7:7 + self.n_actuators]
            diff_q = current_qpos - STAND_REF_QPOS
            weighted_q_mse = float(np.sum(STAND_JOINT_WEIGHTS * (diff_q ** 2)) / np.sum(STAND_JOINT_WEIGHTS))
            r_pose = float(np.exp(-3.0 * weighted_q_mse))

            # 2. Torso Center-of-Mass Height Similarity (centered at z* = 1.168m):
            r_height = float(np.exp(-30.0 * ((z - 1.168) ** 2)))

            # 3. Torso Upright Orientation Similarity:
            r_upright = float(np.exp(-12.0 * (max(0.0, 1.0 - up_z) ** 2)))

            # 4. Multi-Rigid-Body Stillness Similarity (root linear, root angular, joint vel):
            lin_vel_sq = float(np.sum(torso_cvel[3:] ** 2))
            ang_vel_sq = float(np.sum(torso_cvel[:3] ** 2))
            joint_vel_sq = float(np.mean(self.data.qvel[6:6 + self.n_actuators] ** 2))
            r_stillness = float(np.exp(-4.0 * (lin_vel_sq + 0.5 * ang_vel_sq + 0.1 * joint_vel_sq)))

            # 5. Foot Ground Contact Multiplier:
            both_feet_down = bool(touch_r and touch_l)
            one_foot_down = bool(touch_r or touch_l)
            if both_feet_down:
                m_feet = 1.0
            elif one_foot_down:
                m_feet = 0.45
            else:
                m_feet = 0.05

            # 6. Action Control / Effort Penalty:
            r_ctrl = -0.002 * float(np.sum(action ** 2))

            # Bounded Gaussian Similarity Reward (Peak = 14.0/step at quiet standing equilibrium)
            total_reward = m_feet * (4.0 * r_pose + 3.0 * r_height + 3.0 * r_upright + 4.0 * r_stillness) + r_ctrl

            # Track stillness success criteria:
            is_stand_still = bool(
                r_pose > 0.85 and
                r_height > 0.88 and
                r_upright > 0.90 and
                r_stillness > 0.80 and
                both_feet_down
            )
            if is_stand_still:
                self.stand_still_steps += 1
            else:
                self.stand_still_steps = max(0, self.stand_still_steps - 1)

            # Check collision with environmental obstacles/ground using body geoms (head, chest, torso, visor)
            is_obstacle_or_ground_impact = False
            for c_idx in range(self.data.ncon):
                c = self.data.contact[c_idx]
                if (c.geom1 in self.body_impact_geoms and c.geom2 in self.world_obstacle_geoms) or \
                   (c.geom2 in self.body_impact_geoms and c.geom1 in self.world_obstacle_geoms):
                    is_obstacle_or_ground_impact = True
                    break

            terminated = False
            # Clean early termination only when genuinely fallen or severely displaced:
            if z < 0.85 or up_z < 0.55 or is_obstacle_or_ground_impact:
                terminated = True
                total_reward -= 15.0
            elif dist_from_origin > 1.20:
                terminated = True
                total_reward -= 10.0

            # Mastery time limit: 384 steps (~9.6s)
            truncated = (self.current_step >= 384)
            if truncated and (not terminated) and z > 1.10 and both_feet_down:
                total_reward += 50.0  # Mastery bonus for surviving 384 steps upright on both feet

            # Detailed metrics for logging & dashboard
            torso_roll = abs(float(torso_xmat[2, 1]))
            torso_pitch = abs(float(torso_xmat[2, 0]))
            spine_lateral = abs(float(self.data.qpos[self.abdomen_x_qpos]))
            spine_sagittal = abs(float(self.data.qpos[self.abdomen_y_qpos]))

            info = {
                "x_pos": float(x), "y_pos": float(y), "z_pos": float(z),
                "vx": float(vx), "torso_speed": float(torso_speed),
                "furthest_x": float(self.furthest_x), "milestones": 0,
                "waypoint_idx": 0, "waypoint_name": "Quiet Stand Stillness",
                "dist_to_wp": float(dist_from_origin), "waypoints_completed": int(self.stand_still_steps > 150),
                "goals_completed": int(self.stand_still_steps > 150),
                "dist_to_goal": float(dist_from_origin),
                "goal_arrival_radius": 1.20,
                "goal_pos": [0.0, 0.0, 1.168],
                "target_local_pos": [0.0, 0.0, 0.0],
                "gaze_alignment": 1.0,
                "stamina": float(self.stamina), "health": float(self.health), "hunger": float(self.hunger),
                "step": self.current_step, "lidar_grid": self.current_lidar_grid.tolist(),
                "in_leeway": False, "leeway_remaining": 0,
                "stream_mode": "stand", "active_reach_hand": "none", "reach_touches": 0,
                "getup_success": False,
                "both_feet_down": bool(both_feet_down),
                "one_foot_down": bool(one_foot_down),
                "stand_still_score": float(is_stand_still),
                "torso_roll": float(torso_roll),
                "torso_pitch": float(torso_pitch),
                "spine_lateral": float(spine_lateral),
                "spine_sagittal": float(spine_sagittal),
                "r_pose": float(r_pose),
                "r_height": float(r_height),
                "r_upright": float(r_upright),
                "r_stillness": float(r_stillness),
            }
            return self._get_obs(), float(total_reward), terminated, truncated, info

        # ── STREAM 2: FALL RECOVERY (GET-UP) ────────────────────────────────
        elif self.stream_mode == "getup":
            head_z = float(self.data.xpos[self.head_body_id][2])
            delta_head_z = head_z - self.prev_head_z
            self.prev_head_z = head_z

            r_foot_z = float(self.data.xpos[self.r_foot_id][2])
            l_foot_z = float(self.data.xpos[self.l_foot_id][2])
            max_foot_z = max(r_foot_z, l_foot_z)

            # 1. REWARD FOR HEAD & TORSO ELEVATION (Rises vertically, head leads above torso):
            reward_head_elevation = 16.0 * delta_head_z
            reward_torso_elevation = 12.0 * max(0.0, z - self.prev_z)
            reward_head_height = 5.0 * max(0.0, head_z - 0.40)
            reward_head_above_torso = 3.5 * max(0.0, head_z - z)
            reward_upright = 3.0 * max(0.0, up_z - 0.30)

            # 2. MULTI-PHASE GROUND CONTACT SUPPORT (Hands, Knees, Feet):
            both_feet_down = touch_r and touch_l
            one_foot_down = touch_r or touch_l

            # Floor bracing support (head_z < 1.15m): reward hands pushing floor & knees tucked
            reward_hand_brace = 4.0 if (contact_hand and head_z < 1.15) else 0.0
            reward_knee_brace = 3.0 if (contact_knee and head_z < 1.15) else 0.0

            # Standing stage (head_z >= 1.05m): reward planting feet
            if both_feet_down:
                reward_feet_ground = 6.0
            elif one_foot_down:
                reward_feet_ground = 2.0
            elif head_z >= 1.20:
                reward_feet_ground = -1.0 # Only penalize missing foot contact once upright
            else:
                reward_feet_ground = 0.0  # Zero penalty while floor-bound rolling or pushing up!

            # Floor proximity for feet during ground phase
            reward_feet_down = 2.0 * max(0.0, 0.30 - max_foot_z) if head_z < 1.15 else 0.0

            # 3. MITIGATE LEG AIR-FLAILING:
            # Only penalize feet higher than head IF head is actually on the ground and feet are violently kicked up
            feet_above_head = max(0.0, max_foot_z - max(0.40, head_z))
            penalty_shooting_legs = -4.0 * feet_above_head

            # Air-flail penalty only when feet are high in air with zero contact
            penalty_air_flail = -2.0 * max(0.0, max_foot_z - 0.50) if (head_z < 1.0 and not (contact_hand or contact_knee)) else 0.0

            # 4. Energy cost & Arm Windmilling Suppression
            arm_flail_penalty = -0.001 * float(np.sum(np.square(action[15:21])))
            reward_ctrl = -0.001 * torque_cost + arm_flail_penalty
            dist_to_stand_goal = float(np.linalg.norm(self.getup_goal_pos[:2] - np.array([x, y])))
            reward_goal_heading = 2.0 * max(0.0, 1.0 - dist_to_stand_goal / 2.0) if head_z > 1.30 else 0.0

            total_reward = (
                reward_head_elevation +
                reward_torso_elevation +
                reward_head_height +
                reward_head_above_torso +
                reward_upright +
                reward_hand_brace +
                reward_knee_brace +
                reward_feet_ground +
                reward_feet_down +
                penalty_shooting_legs +
                penalty_air_flail +
                reward_ctrl +
                reward_goal_heading
            )
            self.prev_z = z

            # Track peak head elevation for stagnation monitoring
            if head_z > self.max_head_elevation:
                self.max_head_elevation = head_z
                self.getup_stagnant_steps = 0
            else:
                self.getup_stagnant_steps += 1

            # Upright standing with feet planted verification:
            # Requires head up (> 1.35m), torso upright (z > 1.05m, up_z > 0.70), and foot contact
            is_upright = (head_z > 1.35) and (z > 1.05) and (up_z > 0.70) and (one_foot_down or (head_z > 1.45 and z > 1.10))
            if is_upright:
                self.consecutive_upright_steps += 1
                total_reward += 3.0
                if both_feet_down:
                    total_reward += 3.0  # Extra jackpot bonus when BOTH feet are planted!
            else:
                self.consecutive_upright_steps = 0

            # Lenient Ground Collapse Stagnation & Rise Stall Deaths:
            # Tolerates 140 steps (~3.5s) struggling on ground without head elevation
            # Tolerates 180 steps (~4.5s) coordinating knee-tuck and feet planting to reach upright stance
            is_ground_stuck = (head_z < 0.50 and self.getup_stagnant_steps > 140)
            is_stall_stuck = (head_z >= 0.50 and self.consecutive_upright_steps == 0 and self.getup_stagnant_steps > 180)

            terminated = False
            if self.consecutive_upright_steps >= 12:
                total_reward += 100.0  # Upright Recovery Jackpot!
                self.getup_success_count += 1
                terminated = True
            elif is_ground_stuck or is_stall_stuck:
                terminated = True
                total_reward -= 10.0  # Timeout stagnation death

            truncated = (self.current_step >= 280)
            target_pos = self.getup_goal_pos

            info = {
                "x_pos": float(x), "y_pos": float(y), "z_pos": float(z),
                "vx": float(vx), "torso_speed": float(torso_speed),
                "furthest_x": float(self.furthest_x), "milestones": 0,
                "waypoint_idx": 0, "waypoint_name": f"Get-Up ({self.fall_state_type})",
                "dist_to_wp": float(max(0.0, 1.55 - head_z)),
                "waypoints_completed": int(self.consecutive_upright_steps >= 12),
                "goals_completed": int(self.consecutive_upright_steps >= 12),
                "dist_to_goal": float(dist_to_stand_goal),
                "goal_arrival_radius": 0.50,
                "goal_pos": self.getup_goal_pos.tolist(),
                "target_local_pos": (torso_xmat.T @ (target_pos - torso_xpos)).tolist(),
                "gaze_alignment": float(max(0.0, up_z)),
                "stamina": float(self.stamina), "health": float(self.health), "hunger": float(self.hunger),
                "step": self.current_step, "lidar_grid": self.current_lidar_grid.tolist(),
                "in_leeway": False, "leeway_remaining": 0,
                "stream_mode": "getup", "active_reach_hand": "none", "reach_touches": 0,
                "getup_success": bool(self.consecutive_upright_steps >= 12),
                "head_z": float(head_z),
                "both_feet_down": bool(both_feet_down),
            }
            return self._get_obs(), float(total_reward), terminated, truncated, info

        # ── STREAM 2: BILATERAL HAND REACHING (BOLTED BODY) ────────────────
        elif self.stream_mode == "reach":
            # Torso, core, and legs are bolted in neutral athletic upright stance.
            # Control is isolated strictly to the 6 arm actuators reaching for 3D orbs.
            r_h = self.data.geom_xpos[self.r_hand_geom_id]
            l_h = self.data.geom_xpos[self.l_hand_geom_id]
            dist_r = float(np.linalg.norm(r_h - self.reach_target_pos))
            dist_l = float(np.linalg.norm(l_h - self.reach_target_pos))

            # The designated active hand is the hand closer to the target ball
            is_right_target = (self.active_reach_hand == "right")

            if is_right_target:
                active_h = r_h
                wrong_h = l_h
                dist_to_target = dist_r
                dist_inactive = dist_l
                active_body_id = self.r_arm_body_id
                wrong_body_id = self.l_arm_body_id
                active_act = action[15:18]
                wrong_act = action[18:21]
                active_qvel = self.data.qvel[self.arm_dof_indices[0:3]]
                wrong_qvel = self.data.qvel[self.arm_dof_indices[3:6]]
                wrong_qpos = self.data.qpos[self.arm_qpos_indices[3:6]]
                wrong_rest_qpos = np.array([-0.65, 0.0, 0.0], dtype=np.float32)
            else:
                active_h = l_h
                wrong_h = r_h
                dist_to_target = dist_l
                dist_inactive = dist_r
                active_body_id = self.l_arm_body_id
                wrong_body_id = self.r_arm_body_id
                active_act = action[18:21]
                wrong_act = action[15:18]
                active_qvel = self.data.qvel[self.arm_dof_indices[3:6]]
                wrong_qvel = self.data.qvel[self.arm_dof_indices[0:3]]
                wrong_qpos = self.data.qpos[self.arm_qpos_indices[0:3]]
                wrong_rest_qpos = np.array([0.65, 0.0, 0.0], dtype=np.float32)

            # 1. Main reach distance progress and proximity reward
            dist_prog = self.prev_reach_dist - dist_to_target
            reward_reach_prog = 25.0 * dist_prog
            reward_proximity = 6.0 * np.exp(-4.0 * dist_to_target)

            # 2. MASSIVE SPEED EFFICIENCY REWARDS:
            # a) Direct closing velocity vector along the unit ray connecting active hand to target orb
            delta_active_target = self.reach_target_pos - active_h
            dist_hand_target = max(1e-4, float(np.linalg.norm(delta_active_target)))
            u_reach_target = delta_active_target / dist_hand_target
            active_hand_vel = self.data.cvel[active_body_id][3:6]
            v_closing = float(np.dot(active_hand_vel, u_reach_target))
            # Speed efficiency bonus for thrusting active hand toward target
            reward_closing_speed = 4.0 * max(0.0, v_closing)

            # b) Mild latency penalty (encourages prompt reaching)
            penalty_latency = -0.02 * (float(self.steps_on_reach_target) / 40.0)

            # 3. Slight reward for moving the correct hand
            active_hand_speed = float(np.linalg.norm(active_hand_vel))
            active_qvel_mag = float(np.sum(np.abs(active_qvel)))
            reward_correct_motion = 0.15 * min(1.0, active_hand_speed / 0.25) + 0.10 * np.tanh(active_qvel_mag)

            # 4. REGULARIZATION ON INACTIVE HAND (stay neutral and relaxed at side)
            wrong_hand_speed = float(np.linalg.norm(self.data.cvel[wrong_body_id][3:6]))
            penalty_wrong_act = -0.05 * float(np.sum(np.square(wrong_act)))
            penalty_wrong_qvel = -0.05 * float(np.sum(np.abs(wrong_qvel)))
            penalty_wrong_speed = -0.20 * min(1.0, wrong_hand_speed)
            penalty_wrong_raised = -0.50 * max(0.0, float(wrong_h[2]) - 1.28)
            penalty_wrong_posture = -0.20 * min(1.0, float(np.linalg.norm(wrong_qpos - wrong_rest_qpos)))
            penalty_wrong_lead = -0.50 * max(0.0, dist_to_target - dist_inactive)
            penalty_wrong_encroach = -0.50 * max(0.0, 0.35 - dist_inactive)
            penalty_wrong_touch = -2.0 if dist_inactive < 0.14 else 0.0

            # General control penalty on active arm to encourage efficient articulation
            reward_ctrl = -0.001 * float(np.sum(np.square(active_act)))

            self.steps_on_reach_target += 1
            if dist_to_target < self.min_reach_dist:
                self.min_reach_dist = dist_to_target
                self.steps_receding_reach = 0
            elif dist_to_target > self.min_reach_dist + 0.25:
                self.steps_receding_reach += 1

            reward_touch = 0.0
            speed_efficiency_jackpot = 0.0
            if dist_to_target < 0.14:
                # 1. Base touch award
                base_touch = 40.0
                # 2. Speed efficiency jackpot: maximum when acquired in few steps
                speed_efficiency_jackpot = max(0.0, 110.0 - float(self.steps_on_reach_target)) * 0.40
                # 3. Consecutive hit streak multiplier
                touch_streak_bonus = min(30.0, float(self.reach_touches) * 6.0)
                reward_touch = base_touch + speed_efficiency_jackpot + touch_streak_bonus

                self.reach_touches += 1
                self._sample_reach_target()
                is_right_target = (self.active_reach_hand == "right")
                active_h = self.data.geom_xpos[self.r_hand_geom_id] if is_right_target else self.data.geom_xpos[self.l_hand_geom_id]
                dist_to_target = float(np.linalg.norm(active_h - self.reach_target_pos))
                # Reset timers for next target!
                self.steps_on_reach_target = 0
                self.steps_receding_reach = 0
                self.min_reach_dist = dist_to_target

            self.prev_reach_dist = dist_to_target
            total_reward = (
                reward_reach_prog +
                reward_proximity +
                reward_closing_speed +
                reward_correct_motion +
                reward_touch +
                penalty_latency +
                penalty_wrong_act +
                penalty_wrong_qvel +
                penalty_wrong_speed +
                penalty_wrong_raised +
                penalty_wrong_posture +
                penalty_wrong_lead +
                penalty_wrong_encroach +
                penalty_wrong_touch +
                reward_ctrl
            )

            # Lenient Reaching Time Limits:
            # Tolerates 110 steps (~2.75s) per target orb, or 45 steps receding away
            is_reach_timeout = (self.steps_on_reach_target > 110)
            is_reach_receding = (self.steps_receding_reach > 45)

            terminated = False
            if is_reach_timeout or is_reach_receding:
                terminated = True
                total_reward -= 2.0  # Mild timeout penalty

            truncated = (self.current_step >= 384)
            target_pos = self.reach_target_pos

            head_xmat = self.data.xmat[self.head_body_id].reshape(3, 3)
            head_fwd = head_xmat[:, 0]
            delta_head_target = target_pos - self.data.xpos[self.head_body_id]
            cos_gaze = float(np.dot(head_fwd, delta_head_target / max(1e-3, np.linalg.norm(delta_head_target))))

            info = {
                "x_pos": float(x), "y_pos": float(y), "z_pos": float(z),
                "vx": float(vx), "torso_speed": float(torso_speed),
                "furthest_x": float(self.furthest_x), "milestones": 0,
                "waypoint_idx": 0, "waypoint_name": f"Reach ({self.active_reach_hand.upper()})",
                "dist_to_wp": float(dist_to_target), "waypoints_completed": int(self.reach_touches),
                "goals_completed": int(self.reach_touches),
                "dist_to_goal": float(dist_to_target),
                "goal_arrival_radius": 0.14,
                "goal_pos": self.reach_target_pos.tolist(),
                "target_local_pos": (torso_xmat.T @ (target_pos - torso_xpos)).tolist(),
                "gaze_alignment": float(cos_gaze),
                "stamina": float(self.stamina), "health": float(self.health), "hunger": float(self.hunger),
                "step": self.current_step, "lidar_grid": self.current_lidar_grid.tolist(),
                "in_leeway": False, "leeway_remaining": 0,
                "stream_mode": "reach", "active_reach_hand": str(self.active_reach_hand),
                "reach_touches": int(self.reach_touches), "getup_success": False, "stand_still_score": 0.0,
                "wrong_hand_dist": float(dist_inactive), "wrong_hand_touch": bool(dist_inactive < 0.14),
                "wrong_hand_speed": float(wrong_hand_speed),
                "wrong_arm_action_penalty": float(penalty_wrong_act),
                "wrong_arm_raised_penalty": float(penalty_wrong_raised),
                "v_closing": float(v_closing),
                "reward_closing_speed": float(reward_closing_speed),
                "speed_efficiency_jackpot": float(speed_efficiency_jackpot),
            }
            return self._get_obs(), float(total_reward), terminated, truncated, info
        # Target Navigation Vector & Forward Propulsion
        if self.arena_mode:
            target_pos = self.goal_pos
            delta_target = target_pos - torso_xpos
            dist_to_target = float(np.linalg.norm(delta_target))
            dist_xy = float(np.linalg.norm(delta_target[:2]))

            # Check dynamic goal arrival (entering wide arrival radius)
            reward_arrival = 0.0
            if dist_xy < self.goal_arrival_radius:
                self.goals_completed += 1
                # Escalating jackpot for chained consecutive goals: 50 for 1st, 85 for 2nd, 120 for 3rd, 155 for 4th...
                reward_arrival = 50.0 + 35.0 * (self.goals_completed - 1)
                self._sample_new_goal(is_initial=False)
                target_pos = self.goal_pos
                delta_target = target_pos - torso_xpos
                dist_to_target = float(np.linalg.norm(delta_target))
                dist_xy = float(np.linalg.norm(delta_target[:2]))
                self.prev_dist_to_goal = dist_to_target
                dist_delta = 0.0
            else:
                dist_delta = self.prev_dist_to_goal - dist_to_target
                self.prev_dist_to_goal = dist_to_target

            # Leeway period active after goal completion to allow decelerating & turning
            in_leeway = (self.goal_transition_steps > 0)
            if in_leeway:
                self.goal_transition_steps -= 1
                # While turning during leeway, continuously update closest distance baseline to current position
                self.min_dist_to_goal = dist_to_target

            # 1. Distance progress potential (scaled with goal streak) & sharp penalty for moving away
            streak_mult = 1.0 + 0.35 * min(4, self.goals_completed)
            if dist_delta >= 0.0:
                reward_dist_progress = 3.0 * streak_mult * dist_delta
            else:
                # Double penalty for moving further away from target outside of turn leeway
                reward_dist_progress = 0.0 if in_leeway else (6.0 * dist_delta)

            # 2. Penalty for drifting/retreating beyond the closest distance achieved so far (muted in leeway)
            retreat_distance = max(0.0, dist_to_target - self.min_dist_to_goal)
            penalty_retreat = 0.0 if in_leeway else (-3.0 * retreat_distance if retreat_distance > 0.10 else 0.0)

            unit_target_dir = delta_target / max(0.1, dist_to_target)
            vel_towards_target = float(np.dot(torso_cvel[3:], unit_target_dir))
            torso_speed = float(np.linalg.norm(torso_cvel[3:]))

            # 3. Controlled Forward Movement vs Severe Retrograde Penalty
            # Cap forward reward at 1.8 m/s so Olympic sprinting gives no extra reward
            v_eff = min(max(0.0, vel_towards_target), 1.8)
            reward_forward = 3.0 * v_eff * upright_scale
            penalty_retrograde = 0.0 if (vel_towards_target >= 0.0 or in_leeway) else (5.0 * vel_towards_target)

            # 4. Heading guidance velocity (steep negative slope when heading backwards outside leeway)
            if vel_towards_target >= 0.0:
                reward_heading = 1.5 * v_eff * upright_scale
            else:
                reward_heading = 0.0 if in_leeway else (3.0 * vel_towards_target)

            # 5. Speed Regulation Penalty: Penalize reckless overspeeding (> 2.0 m/s) to promote stable locomotion
            penalty_overspeed = 0.0
            if torso_speed > 2.0:
                penalty_overspeed = -3.0 * ((torso_speed - 2.0) ** 2)

            # 6. Turn alignment & braking reward during transition leeway: encourage slowing down & rapid yaw alignment to new goal
            reward_turn = 0.0
            reward_brake = 0.0
            if in_leeway:
                torso_fwd = torso_xmat[:, 0]
                cos_torso_goal = float(np.dot(torso_fwd[:2], unit_target_dir[:2]))
                # Reward rotating body to face new target (+0.0 to +1.0)
                reward_turn = 1.0 * max(0.0, cos_torso_goal)
                # Reward decelerating below 1.6 m/s so the agent can pivot cleanly
                if torso_speed < 1.6:
                    reward_brake = 0.6 * (1.6 - torso_speed)

            # 7. Subsequent Goal Urgency: Time-decay pressure once Goal 1 is cleared
            penalty_urgency = 0.0
            if self.goals_completed >= 1 and not in_leeway:
                penalty_urgency = -0.08 * min(3, self.goals_completed)

            reward_wp = (
                reward_arrival +
                reward_dist_progress +
                penalty_retreat +
                penalty_retrograde +
                penalty_overspeed +
                reward_turn +
                reward_brake +
                penalty_urgency
            )
            reward_drift = 0.0
            reward_milestone = 0.0
            dist_to_wp = dist_to_target
        else:
            # Obstacle course mode
            wp_pos, wp_name, wp_radius = COURSE_WAYPOINTS[self.current_wp_idx]
            target_pos = wp_pos
            delta_to_wp = wp_pos - torso_xpos
            dist_to_wp = float(np.linalg.norm(delta_to_wp))
            dist_xy = float(np.linalg.norm(delta_to_wp[:2]))

            reward_forward = 3.5 * vx * upright_scale
            if vx < -0.05:
                reward_forward += 1.5 * vx

            wp_reached = False
            if dist_xy < wp_radius:
                wp_reached = True
            elif torso_xpos[0] >= wp_pos[0] and abs(torso_xpos[1] - wp_pos[1]) < (wp_radius + 0.3):
                wp_reached = True
                
            reward_wp = 0.0
            if wp_reached and self.current_wp_idx not in self.waypoints_reached:
                self.waypoints_reached.add(self.current_wp_idx)
                if self.current_wp_idx == len(COURSE_WAYPOINTS) - 1:
                    reward_wp = 100.0
                elif 3 <= self.current_wp_idx <= 14:
                    reward_wp = 25.0
                else:
                    reward_wp = 15.0
                if self.current_wp_idx < len(COURSE_WAYPOINTS) - 1:
                    self.current_wp_idx += 1
                    wp_pos, wp_name, wp_radius = COURSE_WAYPOINTS[self.current_wp_idx]
                    target_pos = wp_pos
                    delta_to_wp = wp_pos - torso_xpos
                    dist_to_wp = float(np.linalg.norm(delta_to_wp))

            wp_unit_dir = delta_to_wp / max(0.1, dist_to_wp)
            vel_towards_wp = float(np.dot(torso_cvel[3:], wp_unit_dir))
            reward_heading = 2.0 * max(-0.5, min(vel_towards_wp, 3.5)) * upright_scale

            target_y = float(wp_pos[1])
            reward_drift = -0.5 * abs(y - target_y)

            reward_milestone = 0.0
            for threshold, name in STAGE_MILESTONES:
                if x >= threshold and threshold not in self.milestones_reached:
                    self.milestones_reached.add(threshold)
                    reward_milestone += 50.0

        # Head Gaze Alignment Reward: mild reward for facing objective with head/visor
        head_xmat = self.data.xmat[self.head_body_id].reshape(3, 3)
        head_fwd = head_xmat[:, 0]  # Local X axis of head (forward gaze direction)
        head_pos = self.data.xpos[self.head_body_id]
        delta_head_target = target_pos - head_pos
        dist_head_target = float(np.linalg.norm(delta_head_target))
        u_head_target = delta_head_target / max(1e-3, dist_head_target)
        cos_gaze = float(np.dot(head_fwd, u_head_target))
        reward_gaze = 0.15 * max(0.0, cos_gaze)

        # 2. Upright posture reward (staying balanced above 0.70m)
        reward_upright = 1.0 if z > 0.70 else 0.0
        
        # 3. Upright orientation bonus & active lateral roll stabilization
        roll_y = torso_xmat[1, 2]
        reward_roll = -2.0 * abs(roll_y)
        reward_orient = 0.8 * max(0.0, up_z) + reward_roll

        # Advance speed for biomechanical stepping gating
        forward_vec = torso_xmat[:, 0]
        v_advance = float(np.dot(torso_cvel[3:6], forward_vec)) if self.arena_mode else vx

        # 4. Alternating Bipedal Stepping Cadence
        reward_gait = 0.0
        if z > 0.55 and v_advance > 0.10:
            if touch_r ^ touch_l:
                reward_gait = 2.0 * min(v_advance, 1.5)
            elif touch_r and touch_l:
                reward_gait = -0.4 * min(v_advance, 1.5)

        # 5. Knee Articulation & Stance Stability
        r_knee_q = self.data.qpos[self.r_knee_qpos]
        l_knee_q = self.data.qpos[self.l_knee_qpos]
        reward_knee = 0.0
        if z > 0.55 and v_advance > 0.10:
            if not touch_r:
                if 0.25 <= r_knee_q <= 1.1:
                    reward_knee += 0.3
                elif r_knee_q > 1.6:
                    reward_knee -= 0.5 * (r_knee_q - 1.6)
            if not touch_l:
                if 0.25 <= l_knee_q <= 1.1:
                    reward_knee += 0.3
                elif l_knee_q > 1.6:
                    reward_knee -= 0.5 * (l_knee_q - 1.6)
            if touch_r and r_knee_q < 0.50:
                reward_knee += 0.2
            if touch_l and l_knee_q < 0.50:
                reward_knee += 0.2

        # 6. Swing foot forward velocity bonus
        r_foot_vfwd = float(np.dot(self.data.cvel[self.r_foot_id][3:6], forward_vec)) if self.arena_mode else self.data.cvel[self.r_foot_id][3]
        l_foot_vfwd = float(np.dot(self.data.cvel[self.l_foot_id][3:6], forward_vec)) if self.arena_mode else self.data.cvel[self.l_foot_id][3]
        reward_swing = 0.0
        if z > 0.55 and v_advance > 0.10:
            if not touch_r and r_foot_vfwd > 0.15:
                reward_swing += 0.3 * min(r_foot_vfwd, 2.0)
            if not touch_l and l_foot_vfwd > 0.15:
                reward_swing += 0.3 * min(l_foot_vfwd, 2.0)

        # 7. Thigh Forward Stride Separation
        r_hip_q = self.data.qpos[self.r_hip_qpos]
        l_hip_q = self.data.qpos[self.l_hip_qpos]
        reward_stride = 0.0
        if z > 0.55 and v_advance > 0.10:
            if not touch_r:
                stride_diff = l_hip_q - r_hip_q
                if 0.1 < stride_diff < 1.3:
                    reward_stride = 1.0 * stride_diff
            elif not touch_l:
                stride_diff = r_hip_q - l_hip_q
                if 0.1 < stride_diff < 1.3:
                    reward_stride = 1.0 * stride_diff

        # 8. Bilateral Stance Symmetry (Duty-Cycle Equalizer)
        reward_symmetry = 0.0
        total_contacts = self.r_foot_contact_steps + self.l_foot_contact_steps
        if self.current_step > 10 and total_contacts > 6 and z > 0.55:
            asym = abs(self.r_foot_contact_steps - self.l_foot_contact_steps) / total_contacts
            if asym > 0.20:
                reward_symmetry = -2.0 * (asym - 0.20)

        # 9. Arm Windmilling Suppression (Penalize flailing arms to force balance from core and legs)
        arm_flail_penalty = -0.008 * float(np.sum(np.square(action[15:21])))
        
        # 10. Energy expenditure penalty
        reward_ctrl = -0.0015 * torque_cost + arm_flail_penalty

        total_reward = (
            reward_forward +
            reward_heading +
            reward_wp +
            reward_gaze +
            reward_upright +
            reward_orient +
            reward_gait +
            reward_knee +
            reward_swing +
            reward_stride +
            reward_symmetry +
            reward_ctrl +
            reward_drift +
            reward_milestone
        )

        if self.arena_mode:
            rad_dist = float(np.linalg.norm([x, y]))
            if rad_dist > self.furthest_x:
                self.furthest_x = rad_dist

            if in_leeway:
                # During turning leeway window: reset & do not accumulate moving-away or stagnation counters
                self.steps_not_approaching = 0
                self.negative_vx_steps = 0
                self.steps_since_progress = 0
                self.min_dist_to_goal = dist_to_target
            else:
                # Active approach check: requires advancing toward target (> 0.15 m/s and closing distance)
                is_actively_approaching = (vel_towards_target >= 0.15) and (dist_delta > 0.001)
                if is_actively_approaching:
                    self.steps_not_approaching = 0
                else:
                    self.steps_not_approaching += 1

                # Receding tracker: moving away from target
                is_receding = (vel_towards_target < -0.05) or (dist_delta < -0.003)
                if is_receding:
                    self.negative_vx_steps += 1
                else:
                    self.negative_vx_steps = max(0, self.negative_vx_steps - 1)

                # Record best approach distance
                if dist_to_target < self.min_dist_to_goal:
                    self.min_dist_to_goal = dist_to_target
                    self.steps_since_progress = 0
                else:
                    self.steps_since_progress += 1
        else:
            if x > self.furthest_x:
                self.furthest_x = x

            if x > self.last_progress_x + 0.06:
                self.last_progress_x = x
                self.steps_since_progress = 0
            else:
                self.steps_since_progress += 1

            if vx < -0.15:
                self.negative_vx_steps += 1
            else:
                self.negative_vx_steps = 0

        # ── TERMINATION & TRUNCATION ──────────────────────────────────────────
        # Exact preserved death conditions:
        # 1. Physical collision: head, visor, chest, or upper torso directly impacts the floor/obstacles
        # 2. True collapse: torso center of mass drops below 0.35m or head drops below 0.45m
        # 3. Complete inversion: torso tilted > 81 deg from vertical (up_z < 0.15)
        # 4. Arena boundary departure (|x| > 24m or |y| > 24m) or course lateral departure (|y| > 3.0m)
        # 5. Fast elimination when moving away or not actively approaching target (outside leeway)
        terminated = False

        is_obstacle_or_ground_impact = False
        for c_idx in range(self.data.ncon):
            c = self.data.contact[c_idx]
            g1, g2 = c.geom1, c.geom2
            if (g1 in self.body_impact_geoms and g2 in self.world_obstacle_geoms) or \
               (g2 in self.body_impact_geoms and g1 in self.world_obstacle_geoms):
                is_obstacle_or_ground_impact = True
                break

        head_z = self.data.xpos[self.head_body_id][2]
        is_altitude_collapse = (z < 0.35) or (head_z < 0.45)
        is_tilt_collapse = (up_z < 0.15)
        is_physical_fall = is_obstacle_or_ground_impact or is_altitude_collapse or is_tilt_collapse

        if self.arena_mode:
            is_boundary_departure = (abs(x) > 24.0 or abs(y) > 24.0)

            # FAST KILL TRIGGERS (active outside turning leeway period):
            # 1. Backing away kill: moved away from target for > 25 steps (~0.6s)
            is_moving_away_kill = (not in_leeway) and (self.negative_vx_steps > 25)

            # 2. Retreat distance kill: backed up > 0.40m further than closest approach achieved
            is_retreat_kill = (not in_leeway) and (dist_to_target > self.min_dist_to_goal + 0.40) and (self.current_step > 15)

            # 3. Not actively approaching kill: dawdling, circling, or stationary for > 80 steps (~2.0s)
            is_not_approaching_kill = (not in_leeway) and (self.current_step > 25 and self.steps_not_approaching > 80)

            # 4. Stagnation kill: no new record distance achieved for > 85 steps (~2.125s)
            is_stagnant_kill = (not in_leeway) and (self.current_step > 25 and self.steps_since_progress > 85)

            if is_physical_fall:
                terminated = True
                total_reward -= 20.0
                self.health = max(0.0, self.health - 0.2)
            elif is_boundary_departure:
                terminated = True
                total_reward -= 20.0
            elif is_moving_away_kill or is_retreat_kill:
                terminated = True
                total_reward -= 25.0  # Severe penalty for retreating/moving away from target
            elif is_not_approaching_kill or is_stagnant_kill:
                terminated = True
                total_reward -= 25.0  # Severe penalty for failing to actively approach target

            # Dropped Goal Streak Penalty:
            # If the agent achieved at least 1 goal, but died before reaching the next goal,
            # apply a moderate penalty to encourage multi-goal chaining without negating arrival returns
            if terminated and self.goals_completed >= 1:
                dropped_goal_penalty = -15.0 * (1.0 + 0.2 * min(3, self.goals_completed - 1))
                total_reward += dropped_goal_penalty
        else:
            is_moving_backwards = (x < self.spawn_x - 0.50) or (self.negative_vx_steps > 60)
            is_stagnant = (self.current_step > 50 and self.steps_since_progress > 90)
            is_lateral_departure = (abs(y) > 3.0)

            if is_physical_fall:
                terminated = True
                total_reward -= 20.0
                self.health = max(0.0, self.health - 0.2)
            elif is_moving_backwards:
                terminated = True
                total_reward -= 15.0
            elif is_stagnant:
                terminated = True
                total_reward -= 10.0
            elif is_lateral_departure:
                terminated = True
                total_reward -= 20.0

            if x >= 47.0:
                terminated = True
                total_reward += 200.0

        truncated = (self.current_step >= self.max_steps)

        info = {
            "x_pos": float(x),
            "y_pos": float(y),
            "z_pos": float(z),
            "vx": float(vx),
            "torso_speed": float(torso_speed),
            "furthest_x": float(self.furthest_x),
            "milestones": len(self.milestones_reached),
            "waypoint_idx": int(self.current_wp_idx),
            "waypoint_name": str(COURSE_WAYPOINTS[self.current_wp_idx][1]) if not self.arena_mode else f"Arena Target #{self.goals_completed + 1}",
            "dist_to_wp": float(dist_to_wp),
            "waypoints_completed": len(self.waypoints_reached) if not self.arena_mode else int(self.goals_completed),
            "goals_completed": int(self.goals_completed),
            "dist_to_goal": float(dist_to_wp),
            "goal_arrival_radius": float(self.goal_arrival_radius) if self.arena_mode else 1.0,
            "goal_pos": self.goal_pos.tolist() if self.arena_mode else list(COURSE_WAYPOINTS[self.current_wp_idx][0]),
            "target_local_pos": (torso_xmat.T @ (target_pos - torso_xpos)).tolist(),
            "gaze_alignment": float(cos_gaze),
            "stamina": float(self.stamina),
            "health": float(self.health),
            "hunger": float(self.hunger),
            "step": self.current_step,
            "lidar_grid": self.current_lidar_grid.tolist(),
            "in_leeway": bool(in_leeway) if self.arena_mode else False,
            "leeway_remaining": int(self.goal_transition_steps) if self.arena_mode else 0,
            "stream_mode": "cruise",
            "active_reach_hand": "none",
            "reach_touches": 0,
            "getup_success": False,
            "stand_still_score": 0.0,
        }

        return self._get_obs(), float(total_reward), terminated, truncated, info

    def render_frame(
        self,
        width: int = 480,
        height: int = 320,
        camera_name: str = "behind_cam",
        ghost_datas: Optional[List[Any]] = None,
        ghost_alpha: Optional[float] = None,
    ) -> np.ndarray:
        """
        Renders an RGB numpy image of the current simulation frame.
        Optionally injects translucent ghost avatars into mjvScene for parallel multi-agent swarm visualization.
        """
        if self._renderer is None or self._renderer.width != width or self._renderer.height != height:
            self._renderer = mujoco.Renderer(self.model, height=height, width=width)
            
        self._renderer.update_scene(self.data, camera=camera_name)

        # Inject dynamic course waypoint goal markers into mjvScene
        scene = self._renderer.scene
        identity_mat = np.eye(3).flatten()
        if self.stream_mode == "reach":
            # Stream 3 Reach: Glowing magenta hand target orb + vertical guide line
            rx, ry, rz = float(self.reach_target_pos[0]), float(self.reach_target_pos[1]), float(self.reach_target_pos[2])
            if scene.ngeom < scene.maxgeom:
                dst_orb = scene.geoms[scene.ngeom]
                orb_pos = np.array([rx, ry, rz], dtype=np.float64)
                orb_size = np.array([0.09, 0.09, 0.09], dtype=np.float64)
                orb_rgba = np.array([0.88, 0.20, 0.95, 0.95], dtype=np.float32)  # Radiant Magenta
                mujoco.mjv_initGeom(dst_orb, mujoco.mjtGeom.mjGEOM_SPHERE, orb_size, orb_pos, identity_mat, orb_rgba)
                dst_orb.transparent = 1
                scene.ngeom += 1

            if scene.ngeom < scene.maxgeom:
                dst_guide = scene.geoms[scene.ngeom]
                guide_pos = np.array([rx, ry, max(0.01, rz / 2.0)], dtype=np.float64)
                guide_size = np.array([0.012, max(0.01, rz / 2.0), 0.0], dtype=np.float64)
                guide_rgba = np.array([0.88, 0.20, 0.95, 0.35], dtype=np.float32)
                mujoco.mjv_initGeom(dst_guide, mujoco.mjtGeom.mjGEOM_CYLINDER, guide_size, guide_pos, identity_mat, guide_rgba)
                dst_guide.transparent = 1
                scene.ngeom += 1

        elif self.stream_mode == "getup":
            # Stream 2 Get-Up: Golden upright elevation target disc
            torso_xpos = self.data.xpos[self.torso_body_id]
            tx, ty = float(torso_xpos[0]), float(torso_xpos[1])
            if scene.ngeom < scene.maxgeom:
                dst_target = scene.geoms[scene.ngeom]
                target_pos = np.array([tx, ty, 1.33], dtype=np.float64)
                target_size = np.array([0.25, 0.02, 0.0], dtype=np.float64)
                target_rgba = np.array([0.98, 0.75, 0.15, 0.65], dtype=np.float32)  # Glowing Amber
                mujoco.mjv_initGeom(dst_target, mujoco.mjtGeom.mjGEOM_CYLINDER, target_size, target_pos, identity_mat, target_rgba)
                dst_target.transparent = 1
                scene.ngeom += 1

        elif self.stream_mode == "stand":
            # Stream 1 Stand: Cyan stillness equilibrium ground pad
            if scene.ngeom < scene.maxgeom:
                dst_ring = scene.geoms[scene.ngeom]
                ring_pos = np.array([0.0, 0.0, 0.015], dtype=np.float64)
                ring_size = np.array([0.35, 0.015, 0.0], dtype=np.float64)
                ring_rgba = np.array([0.22, 0.74, 0.97, 0.50], dtype=np.float32)  # Cyan Pad
                mujoco.mjv_initGeom(dst_ring, mujoco.mjtGeom.mjGEOM_CYLINDER, ring_size, ring_pos, identity_mat, ring_rgba)
                dst_ring.transparent = 1
                scene.ngeom += 1

        elif self.arena_mode:
            # ACTIVE ARENA GOAL: Glowing floating target orb + vertical laser beacon column + ground target ring
            gx, gy, gz = float(self.goal_pos[0]), float(self.goal_pos[1]), float(self.goal_pos[2])
            
            # 1. Floating target orb (sphere)
            if scene.ngeom < scene.maxgeom:
                dst_orb = scene.geoms[scene.ngeom]
                orb_pos = np.array([gx, gy, gz + 0.35], dtype=np.float64)
                orb_size = np.array([0.22, 0.22, 0.22], dtype=np.float64)
                orb_rgba = np.array([0.98, 0.75, 0.15, 0.90], dtype=np.float32)  # Vibrant Gold
                mujoco.mjv_initGeom(dst_orb, mujoco.mjtGeom.mjGEOM_SPHERE, orb_size, orb_pos, identity_mat, orb_rgba)
                dst_orb.transparent = 1
                scene.ngeom += 1

            # 2. Vertical laser beacon column (cylinder)
            if scene.ngeom < scene.maxgeom:
                dst_beam = scene.geoms[scene.ngeom]
                beam_pos = np.array([gx, gy, 1.25], dtype=np.float64)
                beam_size = np.array([0.05, 1.25, 0.0], dtype=np.float64)
                beam_rgba = np.array([0.22, 0.74, 0.97, 0.55], dtype=np.float32)  # Glowing Cyan
                mujoco.mjv_initGeom(dst_beam, mujoco.mjtGeom.mjGEOM_CYLINDER, beam_size, beam_pos, identity_mat, beam_rgba)
                dst_beam.transparent = 1
                scene.ngeom += 1

            # 3. Ground target arrival ring
            if scene.ngeom < scene.maxgeom:
                dst_ring = scene.geoms[scene.ngeom]
                ring_pos = np.array([gx, gy, 0.02], dtype=np.float64)
                ring_size = np.array([self.goal_arrival_radius, 0.02, 0.0], dtype=np.float64)
                ring_rgba = np.array([0.22, 0.74, 0.97, 0.45], dtype=np.float32)
                mujoco.mjv_initGeom(dst_ring, mujoco.mjtGeom.mjGEOM_CYLINDER, ring_size, ring_pos, identity_mat, ring_rgba)
                dst_ring.transparent = 1
                scene.ngeom += 1
        else:
            for wp_idx, (wp_coord, wp_name, wp_radius) in enumerate(COURSE_WAYPOINTS):
                if scene.ngeom + 3 >= scene.maxgeom:
                    break
                wx = float(wp_coord[0])
                wy = float(wp_coord[1])
                wz = float(wp_coord[2])

                if wp_idx == self.current_wp_idx:
                    # ACTIVE GOAL: Glowing floating target orb + vertical laser beacon column + ground target ring
                    # 1. Floating target orb (sphere)
                    dst_orb = scene.geoms[scene.ngeom]
                    orb_pos = np.array([wx, wy, wz + 0.35], dtype=np.float64)
                    orb_size = np.array([0.18, 0.18, 0.18], dtype=np.float64)
                    orb_rgba = np.array([0.98, 0.75, 0.15, 0.90], dtype=np.float32) # Vibrant Gold
                    mujoco.mjv_initGeom(dst_orb, mujoco.mjtGeom.mjGEOM_SPHERE, orb_size, orb_pos, identity_mat, orb_rgba)
                    dst_orb.transparent = 1
                    scene.ngeom += 1

                    # 2. Vertical laser beacon column (cylinder)
                    if scene.ngeom < scene.maxgeom:
                        dst_beam = scene.geoms[scene.ngeom]
                        beam_pos = np.array([wx, wy, wz + 0.60], dtype=np.float64)
                        beam_size = np.array([0.05, 0.60, 0.0], dtype=np.float64)
                        beam_rgba = np.array([0.22, 0.74, 0.97, 0.55], dtype=np.float32) # Glowing Cyan
                        mujoco.mjv_initGeom(dst_beam, mujoco.mjtGeom.mjGEOM_CYLINDER, beam_size, beam_pos, identity_mat, beam_rgba)
                        dst_beam.transparent = 1
                        scene.ngeom += 1

                    # 3. Ground target landing pad ring
                    if scene.ngeom < scene.maxgeom:
                        dst_ring = scene.geoms[scene.ngeom]
                        ring_pos = np.array([wx, wy, max(0.01, wz - 0.05)], dtype=np.float64)
                        ring_size = np.array([float(wp_radius) * 0.6, 0.02, 0.0], dtype=np.float64)
                        ring_rgba = np.array([0.22, 0.74, 0.97, 0.45], dtype=np.float32)
                        mujoco.mjv_initGeom(dst_ring, mujoco.mjtGeom.mjGEOM_CYLINDER, ring_size, ring_pos, identity_mat, ring_rgba)
                        dst_ring.transparent = 1
                        scene.ngeom += 1

                elif wp_idx < self.current_wp_idx:
                    # COMPLETED GOAL: Subtle emerald disc on surface
                    dst_comp = scene.geoms[scene.ngeom]
                    comp_pos = np.array([wx, wy, max(0.01, wz - 0.05)], dtype=np.float64)
                    comp_size = np.array([0.25, 0.015, 0.0], dtype=np.float64)
                    comp_rgba = np.array([0.10, 0.85, 0.35, 0.40], dtype=np.float32) # Emerald Green
                    mujoco.mjv_initGeom(dst_comp, mujoco.mjtGeom.mjGEOM_CYLINDER, comp_size, comp_pos, identity_mat, comp_rgba)
                    dst_comp.transparent = 1
                    scene.ngeom += 1

                else:
                    # UPCOMING GOAL: Translucent waypoint marker disc
                    dst_up = scene.geoms[scene.ngeom]
                    up_pos = np.array([wx, wy, max(0.01, wz - 0.05)], dtype=np.float64)
                    up_size = np.array([0.16, 0.015, 0.0], dtype=np.float64)
                    up_rgba = np.array([0.60, 0.65, 0.80, 0.25], dtype=np.float32) # Translucent Silver
                    mujoco.mjv_initGeom(dst_up, mujoco.mjtGeom.mjGEOM_CYLINDER, up_size, up_pos, identity_mat, up_rgba)
                    dst_up.transparent = 1
                    scene.ngeom += 1

        # Inject translucent ghost avatars if provided
        if ghost_datas:
            scene = self._renderer.scene
            for g_idx, g_data in enumerate(ghost_datas):
                color = GHOST_PALETTE[g_idx % len(GHOST_PALETTE)]
                if ghost_alpha is not None:
                    color = color.copy()
                    color[3] = float(ghost_alpha)
                for gid in self.humanoid_geoms:
                    if scene.ngeom >= scene.maxgeom:
                        break
                    dst = scene.geoms[scene.ngeom]
                    pos = g_data.geom_xpos[gid].astype(np.float64)
                    size = self.model.geom_size[gid].astype(np.float64)
                    mat = g_data.geom_xmat[gid].astype(np.float64)
                    geom_type = int(self.model.geom_type[gid])

                    mujoco.mjv_initGeom(dst, geom_type, size, pos, mat, color)
                    dst.transparent = 1
                    scene.ngeom += 1

        return self._renderer.render()