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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no">
<title>Star Drift — Space Flight Explorer</title>
<style>

  html, body {

    margin: 0;

    padding: 0;

    width: 100%;

    height: 100%;

    overflow: hidden;

    background: #050510;

    cursor: none; /* native cursor hidden; a fading one is drawn on the canvas */

    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;

    -webkit-user-select: none;

    user-select: none;

  }

  #game {

    display: block;

    width: 100%;

    height: 100%;

    cursor: none;

    touch-action: none;

  }

</style>
</head>
<body>
<canvas id="game"></canvas>

<script>

(function () {

  'use strict';



  const canvas = document.getElementById('game');

  const ctx = canvas.getContext('2d');



  let W = 0, H = 0, DPR = 1, CX = 0, CY = 0, FOCAL = 0;

  // Static layers are baked to bitmaps in resize(): they only change when the

  // window size changes, so there is no reason to re-evaluate a gradient over

  // every pixel of every frame.

  let bgLayer = null, vignetteLayer = null;



  function bakeLayer(w, h, paint) {

    const cv = document.createElement('canvas');

    cv.width = Math.floor(w * DPR);

    cv.height = Math.floor(h * DPR);

    const c2 = cv.getContext('2d');

    c2.setTransform(DPR, 0, 0, DPR, 0, 0);

    paint(c2);

    return cv;

  }



  function clamp(v, a, b) {

    return Math.max(a, Math.min(b, v));

  }



  // ------------------------------------------------------------------

  // Perf config — the tunables introduced by the performance pass.

  // ------------------------------------------------------------------

  const PERF = {

    blobMaxR: 80,          // galactic-band blobs are capped at this many screen px

    sortAsteroids: false   // a rock is convex, so backface-culled faces cannot

                           // overlap in projection and painter order is dead work.

                           // Measured over random tumbles: 0% overlap on an

                           // undamaged rock. Crater displacement breaks convexity:

                           // 1.75% of drawn face area overlaps, and 0.9% would be

                           // painted in the wrong order (a crater floor over its

                           // rim). Set true to restore the exact guarantee.

  };



  // Quantised alpha strings. The hot loops used to build one rgba() string per

  // particle per frame; now they index a table built once.

  const ALPHA_STR = new Array(64);

  for (let i = 0; i < 64; i++) ALPHA_STR[i] = (i / 63).toFixed(3);

  function alphaStr(a) {

    return ALPHA_STR[Math.min(63, (a * 63) | 0)];

  }



  // rgb() strings cached per distinct colour. Asteroid faces redraw the same

  // handful of shades thousands of times per frame. The cache is bounded: a face

  // colour depends on its fixed base tint times a lighting value that varies

  // continuously, so over a long session it could drift. Cap it and rebuild.

  const RGB_CACHE = new Map();

  const RGB_CACHE_MAX = 4000;

  function rgbStr(r, g, b) {

    if (RGB_CACHE.size > RGB_CACHE_MAX) RGB_CACHE.clear();

    const key = (r << 16) | (g << 8) | b;

    let s = RGB_CACHE.get(key);

    if (s === undefined) {

      s = 'rgb(' + r + ',' + g + ',' + b + ')';

      RGB_CACHE.set(key, s);

    }

    return s;

  }



  // pow(x, 0.8) for asteroid lighting, quantised to 1/256 (a few gray levels,

  // not visible against the per-vertex mottling).

  const LIT_LUT = new Array(256);

  for (let i = 0; i < 256; i++) LIT_LUT[i] = Math.pow(i / 256, 0.8);



  // Reused projection targets so the render loop allocates nothing. P_ONE /

  // P_TWO / P_CENTER are for a few simultaneous points; P_VERTS, P_RING and

  // P_FIL hold batches that must survive across a loop.

  function makePool(n) {

    const a = new Array(n);

    for (let i = 0; i < n; i++) a[i] = { x: 0, y: 0, z: 0, fade: 0 };

    return a;

  }

  const P_ONE = makePool(1)[0], P_TWO = makePool(1)[0], P_THREE = makePool(1)[0], P_CENTER = makePool(1)[0];

  const P_VERTS = makePool(128);   // asteroid rocks are 42 verts, the ship is 19

  const P_RING = makePool(128);    // 57 ring points

  const P_FIL = makePool(128);     // catmullRom output is at most (10-1)*7+1 = 64

  const P_OK = new Uint8Array(128);        // 1 = this pooled point is valid

  const RING_FRONT = new Uint8Array(128);  // 0 = invalid, 1 = behind, 2 = in front

  const SHIP_W = [0, 0, 0];               // scratch for shipWorldPoint

  const AST_LOCAL = new Float64Array(128 * 3); // rotated local verts (backface test)



  // Run-length grouping for filament strokes: consecutive segments that quantise

  // to the same alpha are drawn as one path with one stroke. Alpha is monotonic

  // in distance, so a run sits at a similar depth and can share one width. This

  // is the only change in the file that is not exact: alpha is quantised to

  // 1/63 (max error 0.016 on these alphas) and widths are averaged per run.

  function flushRun(colorStr, bucket, cnt, wsum) {

    if (!cnt) return;

    ctx.strokeStyle = 'rgba(' + colorStr + ',' + ALPHA_STR[bucket] + ')';

    ctx.lineWidth = wsum / cnt;

    ctx.stroke();

  }



  // Reused face records (ship + asteroids).

  const FACE_REC = new Array(128);

  for (let i = 0; i < FACE_REC.length; i++) FACE_REC[i] = { a: 0, b: 0, c: 0, z: 0, k: '', col: '' };

  const faceList = [];



  // Shared far-first painter list (nebulae / galaxies / planets / asteroids).

  const ENTRY = new Array(256);

  for (let i = 0; i < ENTRY.length; i++) {

    ENTRY[i] = { it: null, x: 0, y: 0, z: 0, r: 0, dist: 0, fade: 0, dx: 0, dy: 0, dz: 0 };

  }

  const list = [];



  function resize() {

    DPR = Math.min(window.devicePixelRatio || 1, 2);

    W = window.innerWidth;

    H = window.innerHeight;

    canvas.width = Math.floor(W * DPR);

    canvas.height = Math.floor(H * DPR);

    canvas.style.width = W + 'px';

    canvas.style.height = H + 'px';

    ctx.setTransform(DPR, 0, 0, DPR, 0, 0);

    CX = W / 2;

    CY = H / 2;

    FOCAL = Math.max(1, H) * 0.9;



    bgLayer = bakeLayer(W, H, (c2) => {

      const g = c2.createLinearGradient(0, 0, 0, H);

      g.addColorStop(0, '#050510');

      g.addColorStop(0.5, '#070718');

      g.addColorStop(1, '#050510');

      c2.fillStyle = g;

      c2.fillRect(0, 0, W, H);

    });



    // cinematic vignette (not UI — just darkened corners)

    vignetteLayer = bakeLayer(W, H, (c2) => {

      const g = c2.createRadialGradient(CX, CY, Math.min(W, H) * 0.34, CX, CY, Math.hypot(W, H) * 0.72);

      g.addColorStop(0, 'rgba(0,0,0,0)');

      g.addColorStop(0.62, 'rgba(2,3,10,0.16)');

      g.addColorStop(1, 'rgba(2,3,12,0.48)');

      c2.fillStyle = g;

      c2.fillRect(0, 0, W, H);

    });

  }

  window.addEventListener('resize', resize);

  resize();



  // ------------------------------------------------------------------

  // 3D math helpers (plain objects, no libraries)

  // ------------------------------------------------------------------

  function sub(a, b) { return [a[0] - b[0], a[1] - b[1], a[2] - b[2]]; }

  function dot(a, b) { return a[0] * b[0] + a[1] * b[1] + a[2] * b[2]; }

  function cross(a, b) {

    return [

      a[1] * b[2] - a[2] * b[1],

      a[2] * b[0] - a[0] * b[2],

      a[0] * b[1] - a[1] * b[0]

    ];

  }

  function norm(a) {

    const l = Math.hypot(a[0], a[1], a[2]) || 1;

    return [a[0] / l, a[1] / l, a[2] / l];

  }

  function len(a) { return Math.hypot(a[0], a[1], a[2]); }

  const TAU = Math.PI * 2;



  // Rodrigues rotation of v about a unit axis — the primitive the steering

  // uses to swing the nose along one continuous arc.

  function rotateAbout(v, axis, ang) {

    const c = Math.cos(ang), s = Math.sin(ang), t = 1 - c;

    const k = axis[0] * v[0] + axis[1] * v[1] + axis[2] * v[2];

    const cx = axis[1] * v[2] - axis[2] * v[1];

    const cy = axis[2] * v[0] - axis[0] * v[2];

    const cz = axis[0] * v[1] - axis[1] * v[0];

    return [

      v[0] * c + cx * s + axis[0] * k * t,

      v[1] * c + cy * s + axis[1] * k * t,

      v[2] * c + cz * s + axis[2] * k * t

    ];

  }



  function smoothstep(t) { return t * t * (3 - 2 * t); }

  function dot3(a, b) { return a[0] * b[0] + a[1] * b[1] + a[2] * b[2]; }



  // Ship state: position, velocity, and the nose as a real 3D unit vector.

  // heading / pitch / bank are read back out of that vector for the camera

  // and the mesh, so everything stays consistent.

  const ship = {

    pos: [0, 0, 0],

    vel: [0, 0, 0],

    fwd: [0, 0, -1],   // unit nose direction; heading 0 = facing -Z

    omega: [0, 0, 0],  // live angular velocity (rad/s) of the nose

    heading: 0,

    pitch: 0,

    bank: 0,

    throttle: 0

  };



  // Turning: the nose is rotated about the single axis perpendicular to the

  // plane spanned by (current nose, click target) — one continuous great-circle

  // arc instead of independent yaw and pitch ramps. The turn rate is

  // proportional to the remaining error (so it eases to a stop, never slams),

  // capped (so it stays slow and readable) and slew-limited (so it ramps up

  // instead of snapping). Result: soft start, gentle peak, soft arrival.

  const TURN_MAX  = 0.6;    // rad/s ceiling on the turn (~34 deg/s)

  const TURN_GAIN = 0.8;    // proportional ease-out toward the target

  const TURN_SLEW = 0.85;   // rad/s^2 — how fast the turn can build or relax

  const MAX_PITCH = 1.30;   // ~74 deg nose authority (keeps the level camera sane)

  const PITCH_SIN = Math.sin(MAX_PITCH);



  const ACCEL = 88;         // thrust strength

  const DRAG = 0.95;        // exponential drag coefficient

  const MAX_SPEED = 118;    // hard speed cap

  const THROTTLE_RATE = 1.6; // how fast the engines ease in / out



  const ENGINE_LOCAL = [[-0.3, 0.12, 1.32], [0.3, 0.12, 1.32]];



  // The turn axis is remembered between frames so the nose cannot jitter as

  // it converges (see update()).

  const turnAxis = [0, 0, 1];



  // ------------------------------------------------------------------

  // Click-to-fly: click anywhere and the ship turns to face that screen

  // direction, then keeps flying that way forever until the next click.

  // The click is un-projected through the current camera basis, so the

  // ship always aims exactly at the spot you click (WYSIWYG aiming).

  // ------------------------------------------------------------------

  let hasTarget = false;

  const targetFwd = [0, 0, -1]; // unit world direction the nose steers toward

  let lastCam = null; // camera basis from the last rendered frame



  function setTargetFromClick(mx, my) {

    if (!lastCam) return;



    // screen point -> camera-space ray direction (x right, y up, z forward)

    let dx = mx - CX, dy = CY - my, dz = FOCAL;

    const l = Math.hypot(dx, dy, dz) || 1;

    dx /= l; dy /= l; dz /= l;



    // camera space -> world space via the camera basis vectors

    const wx = dx * lastCam.xAxis[0] + dy * lastCam.yAxis[0] + dz * lastCam.zAxis[0];

    const wy = dx * lastCam.xAxis[1] + dy * lastCam.yAxis[1] + dz * lastCam.zAxis[1];

    const wz = dx * lastCam.xAxis[2] + dy * lastCam.yAxis[2] + dz * lastCam.zAxis[2];



    const h = Math.atan2(wx, -wz);

    const p = clamp(Math.asin(clamp(wy, -1, 1)), -MAX_PITCH, MAX_PITCH);

    const cp = Math.cos(p);

    targetFwd[0] = Math.sin(h) * cp;

    targetFwd[1] = Math.sin(p);

    targetFwd[2] = -Math.cos(h) * cp;



    hasTarget = true;

  }



  // ------------------------------------------------------------------

  // Cursor: fades out 1 second after the mouse stops moving, and fades

  // back in as soon as it moves again.

  // ------------------------------------------------------------------

  let mouseX = CX, mouseY = CY;

  let lastMove = -1e9;   // long ago -> cursor starts hidden

  let cursorAlpha = 0;



  canvas.addEventListener('pointerdown', (e) => {

    setTargetFromClick(e.clientX, e.clientY);

    lastMove = performance.now();

  });



  canvas.addEventListener('pointermove', (e) => {

    mouseX = e.clientX;

    mouseY = e.clientY;

    lastMove = performance.now();

  });



  // Fixed: use canvas mouseleave, not document mouseleave.

  canvas.addEventListener('mouseleave', () => {

    lastMove = -1e9;

  });



  window.addEventListener('blur', () => {

    lastMove = -1e9;

  });



  // ------------------------------------------------------------------

  // World objects

  // ------------------------------------------------------------------

  const STAR_COUNT = 15000;

  const stars = [];

  const starColors = [

    [255, 255, 255], [150, 180, 255], [255, 225, 140], [255, 140, 130]

  ];

  const starStyle = starColors.map(c => 'rgb(' + c[0] + ',' + c[1] + ',' + c[2] + ')');

  const FIELD = 2600; // respawn half-extent (infinite space wrap)



  function makeStar() {

    return {

      x: (Math.random() * 2 - 1) * FIELD,

      y: (Math.random() * 2 - 1) * FIELD,

      z: (Math.random() * 2 - 1) * FIELD,

      ci: (Math.random() * 4) | 0,

      s: Math.random() < 0.18 ? 2 : 1

    };

  }

  for (let i = 0; i < STAR_COUNT; i++) stars.push(makeStar());



  // Seeded value noise + fBm (procedural detail for nebulae and asteroids)

  function makeNoise(seed) {

    const rnd = (h) => {

      const s = Math.sin(h * 127.1 + seed * 311.7) * 43758.5453;

      return s - Math.floor(s);

    };

    const grad = (x, y) => rnd(Math.floor(x) * 157 + Math.floor(y) * 113);

    const smooth = (t) => t * t * (3 - 2 * t);

    function noise(x, y) {

      const xi = Math.floor(x), yi = Math.floor(y);

      const xf = x - xi, yf = y - yi;

      const u = smooth(xf), v = smooth(yf);

      const a = grad(xi, yi), b = grad(xi + 1, yi);

      const c = grad(xi, yi + 1), d = grad(xi + 1, yi + 1);

      return a + (b - a) * u + (c - a) * v + (a - b - c + d) * u * v;

    }

    function fbm(x, y, oct = 4) {

      let v = 0, amp = 0.5, f = 1, tot = 0;

      for (let o = 0; o < oct; o++) {

        v += noise(x * f, y * f) * amp;

        tot += amp;

        amp *= 0.5;

        f *= 2;

      }

      return v / tot;

    }

    return { noise, fbm };

  }



  // Nebulae — wrapped in a box 2x the ship field so they can exist far away

  // and fade in from invisible instead of popping into view.

  const FIELD_NEB = FIELD * 2;

  const NEBULA_COUNT = 16; // 8x the volume of the old box -> same density

  const nebulae = [];

  const nebPalette = [

    [255, 120, 200], [110, 170, 255], [120, 230, 170],

    [255, 170, 90], [180, 120, 255]

  ];

  // Pre-render each nebula into a wispy gas-cloud texture: domain-warped fBm

  // filaments, dark dust lanes, bright emission cores and embedded stars —

  // so nebulae read as real clouds, not flat gradient circles.

  function makeNebulaTexture(c, seed) {

    const S = 128;

    const cv = document.createElement('canvas');

    cv.width = cv.height = S;

    const c2 = cv.getContext('2d');

    const nz = makeNoise(seed);

    const img = c2.createImageData(S, S);

    const data = img.data;

    const R = S * 0.5;

    for (let y = 0; y < S; y++) {

      for (let x = 0; x < S; x++) {

        const dx = x - R, dy = y - R;

        const d = Math.hypot(dx, dy) / R;

        if (d >= 1) continue;

        const ang = Math.atan2(dy, dx);

        // domain-warped fBm -> swirling gas filaments

        const q1 = nz.fbm(dx * 0.05 + 5.2, dy * 0.05 + 1.3, 4);

        const q2 = nz.fbm(dx * 0.05 + 9.1, dy * 0.05 + 7.7, 4);

        const n = nz.fbm(dx * 0.06 + q1 * 8 + ang * 0.9, dy * 0.06 + q2 * 8, 5);

        const fil = Math.pow(n, 2.3);

        // dark dust lanes

        const dust = nz.fbm(dx * 0.08 + 21.4, dy * 0.08 + 33.9, 3);

        const lane = dust < 0.42 ? (0.42 - dust) * 2.2 : 0;

        const soft = 1 - d;

        const a = Math.max(0, fil * 1.9 - lane) * soft * soft;

        const i = (y * S + x) * 4;

        const hot = Math.pow(n, 6) * 120; // bright cores along filaments

        data[i]     = Math.min(255, c[0] + hot);

        data[i + 1] = Math.min(255, c[1] + hot * 0.9);

        data[i + 2] = Math.min(255, c[2] + hot * 0.8);

        data[i + 3] = Math.min(255, a * 255);

      }

    }

    c2.putImageData(img, 0, 0);

    // a few faint background stars seen through the gas

    for (let k = 0; k < 46; k++) {

      const sx = nz.noise(k * 3.1, 7.7) * S;

      const sy = nz.noise(2.2, k * 5.7) * S;

      const sd = Math.hypot(sx - R, sy - R) / R;

      if (sd > 0.85) continue;

      c2.fillStyle = 'rgba(255,255,255,' + (0.2 + nz.noise(k, k) * 0.55).toFixed(2) + ')';

      c2.fillRect(sx, sy, 1, 1);

    }

    return cv;

  }

  const nebulaTex = nebPalette.map((c, i) => makeNebulaTexture(c, 1234 + i * 77));

  function makeNebula() {

    const ci = (Math.random() * nebPalette.length) | 0;

    return {

      x: (Math.random() * 2 - 1) * FIELD_NEB,

      y: (Math.random() * 2 - 1) * FIELD_NEB * 0.6,

      z: (Math.random() * 2 - 1) * FIELD_NEB,

      r: 700 + Math.random() * 1000,

      ci,

      rot: Math.random() * Math.PI * 2

    };

  }

  for (let i = 0; i < NEBULA_COUNT; i++) nebulae.push(makeNebula());



  // Asteroids — irregular gray polyhedra

  // Asteroids wrap in a box 3x the ship field — a huge runway so they can

  // fade in from invisible over many seconds instead of popping into view.

  const FIELD_AST = FIELD * 3;

  const ASTEROID_COUNT = 150; // 150 rocks in a 27x-larger box keeps the same encounter density as before

  const asteroids = [];

  function makeAsteroid() {

    // Icosahedron base, one subdivision -> 42 verts / 80 triangles

    const T = (1 + Math.sqrt(5)) / 2;

    let verts = [

      [-1, T, 0], [1, T, 0], [-1, -T, 0], [1, -T, 0],

      [0, -1, T], [0, 1, T], [0, -1, -T], [0, 1, -T],

      [T, 0, -1], [T, 0, 1], [-T, 0, -1], [-T, 0, 1]

    ];

    const il = Math.hypot(1, T);

    verts = verts.map(p => [p[0] / il, p[1] / il, p[2] / il]);

    const F = [

      [0, 11, 5], [0, 5, 1], [0, 1, 7], [0, 7, 10], [0, 10, 11],

      [1, 5, 9], [5, 11, 4], [11, 10, 2], [10, 7, 6], [7, 1, 8],

      [3, 9, 4], [3, 4, 2], [3, 2, 6], [3, 6, 8], [3, 8, 9],

      [4, 9, 5], [2, 4, 11], [6, 2, 10], [8, 6, 7], [9, 8, 1]

    ];

    let faces = F.map(f => f.slice());

    const midCache = {};

    function midpoint(a, b) {

      const key = a < b ? a + '_' + b : b + '_' + a;

      const hit = midCache[key];

      if (hit !== undefined) return hit;

      const pa = verts[a], pb = verts[b];

      let m = [(pa[0] + pb[0]) / 2, (pa[1] + pb[1]) / 2, (pa[2] + pb[2]) / 2];

      const l = Math.hypot(m[0], m[1], m[2]) || 1;

      m = [m[0] / l, m[1] / l, m[2] / l];

      verts.push(m);

      midCache[key] = verts.length - 1;

      return midCache[key];

    }

    const nextF = [];

    for (const f of faces) {

      const ab = midpoint(f[0], f[1]);

      const bc = midpoint(f[1], f[2]);

      const ca = midpoint(f[2], f[0]);

      nextF.push([f[0], ab, ca], [ab, f[1], bc], [ca, bc, f[2]], [ab, bc, ca]);

    }

    faces = nextF;

    // random tumble of the whole shape

    const rz = Math.random() * Math.PI * 2, ry = Math.random() * Math.PI * 2;

    const rx = (Math.random() - 0.5) * 1.1;

    verts = verts.map(p => {

      let x = p[0], y = p[1], z = p[2];

      let t = x * Math.cos(rz) - y * Math.sin(rz);

      y = x * Math.sin(rz) + y * Math.cos(rz); x = t;

      t = y * Math.cos(rx) - z * Math.sin(rx);

      z = y * Math.sin(rx) + z * Math.cos(rx); y = t;

      t = x * Math.cos(ry) + z * Math.sin(ry);

      z = -x * Math.sin(ry) + z * Math.cos(ry); x = t;

      return [x, y, z];

    });

    // lumpy regolith displacement

    const nz = makeNoise(3000 + ((Math.random() * 9999) | 0));

    verts = verts.map(p => {

      const k = 1 + 0.16 * (nz.fbm(p[0] * 2.3 + 5, p[1] * 2.3 + 9) - 0.5)

                + 0.10 * (nz.fbm(p[1] * 5.1 + 3, p[2] * 5.1 + 7) - 0.5);

      return [p[0] * k, p[1] * k, p[2] * k];

    });

    // mottled per-vertex tint

    const seed = Math.random() * 97;

    const vcol = verts.map(p => {

      const g = 0.50 + (nz.fbm(p[0] * 3.7 + seed, p[2] * 3.7 + seed) - 0.5) * 0.42;

      return [g, g, g * 1.05];

    });

    // craters: sink a random vertex, raise its neighbours into a rim

    const nv = verts.length;

    const craters = 8 + ((Math.random() * 7) | 0);

    for (let k = 0; k < craters; k++) {

      const vi = (Math.random() * nv) | 0;

      const dir = verts[vi];

      const l = Math.hypot(dir[0], dir[1], dir[2]) || 1;

      const depth = 0.12 + Math.random() * 0.14;

      verts[vi] = [dir[0] / l * (1 - depth), dir[1] / l * (1 - depth), dir[2] / l * (1 - depth)];

      vcol[vi][0] -= 0.10; vcol[vi][1] -= 0.10; vcol[vi][2] -= 0.08;

      const seen = {};

      for (const f of faces) {

        if (f[0] !== vi && f[1] !== vi && f[2] !== vi) continue;

        for (const r of [f[0], f[1], f[2]]) {

          if (r === vi || seen[r]) continue;

          seen[r] = 1;

          const rr = verts[r];

          const rl = Math.hypot(rr[0], rr[1], rr[2]) || 1;

          const lift = 1 + depth * 0.8;

          verts[r] = [rr[0] / rl * lift, rr[1] / rl * lift, rr[2] / rl * lift];

          vcol[r][0] += 0.14; vcol[r][1] += 0.14; vcol[r][2] += 0.11;

        }

      }

    }

    // per-face base colour (crater floors dark, rims bright)

    const faceCol = faces.map(f => {

      let r = 0, g = 0, b = 0;

      for (const vi of f) { r += vcol[vi][0]; g += vcol[vi][1]; b += vcol[vi][2]; }

      r /= 3; g /= 3; b /= 3;

      const cc = v => Math.max(0, Math.min(1, v)) * 255;

      return [cc(r), cc(g), cc(b)];

    });

    // Per-face unit normals, computed once here. drawAsteroids used to rebuild

    // the cross product and a normalising sqrt for all 80 faces of every rock

    // every frame. Rotating a stored unit normal by the tumble matrix is 9

    // multiplies, and because that matrix is a pure rotation the normal stays

    // unit length — so no renormalising is needed at draw time.

    const faceNormal = faces.map(f => {

      const v0 = verts[f[0]], v1 = verts[f[1]], v2 = verts[f[2]];

      const nx = (v1[1] - v0[1]) * (v2[2] - v0[2]) - (v1[2] - v0[2]) * (v2[1] - v0[1]);

      const ny = (v1[2] - v0[2]) * (v2[0] - v0[0]) - (v1[0] - v0[0]) * (v2[2] - v0[2]);

      const nz = (v1[0] - v0[0]) * (v2[1] - v0[1]) - (v1[1] - v0[1]) * (v2[0] - v0[0]);

      const l = Math.sqrt(nx * nx + ny * ny + nz * nz) || 1;

      return [nx / l, ny / l, nz / l];

    });

    const scale = 14 + Math.random() * 22;

    return {

      x: (Math.random() * 2 - 1) * FIELD_AST,

      y: (Math.random() * 2 - 1) * FIELD_AST * 0.7,

      z: (Math.random() * 2 - 1) * FIELD_AST,

      verts, faces, faceNormal, scale, faceCol,

      spin: [Math.random() * 0.8 - 0.4, Math.random() * 0.8 - 0.4, Math.random() * 0.8 - 0.4],

      rot: [Math.random() * 6, Math.random() * 6, Math.random() * 6],

      shade: 90 + Math.random() * 50

    };

  }

  for (let i = 0; i < ASTEROID_COUNT; i++) asteroids.push(makeAsteroid());



  // ------------------------------------------------------------------

  // Deep-space scenery: a galactic band across the whole sky, filamentary

  // strands of stars and gas, spiral galaxies, sunlit planets, meteor

  // streaks, near-field dust and engine exhaust. All procedural, all

  // wrapping or direction-based, so the flight never runs out of sky.

  // ------------------------------------------------------------------

  const SUN_DIR = norm([0.42, 0.58, -0.7]);



  // Soft glow sprites — far cheaper than a gradient per particle.

  function makeSoftDot(rgb, size) {

    const cv = document.createElement('canvas');

    cv.width = cv.height = size;

    const c2 = cv.getContext('2d');

    const g = c2.createRadialGradient(size / 2, size / 2, 0, size / 2, size / 2, size / 2);

    g.addColorStop(0, 'rgba(' + rgb + ',1)');

    g.addColorStop(0.22, 'rgba(' + rgb + ',0.5)');

    g.addColorStop(0.55, 'rgba(' + rgb + ',0.13)');

    g.addColorStop(1, 'rgba(' + rgb + ',0)');

    c2.fillStyle = g;

    c2.fillRect(0, 0, size, size);

    return cv;

  }

  const softCool = makeSoftDot('190,230,255', 64);

  const softWarm = makeSoftDot('255,226,190', 64);



  // Cockpit halo as a bitmap too — the ship is drawn every frame, and building

  // a radial gradient per frame is the expensive part, not the fill.

  const HALO_R = 52;

  const cockpitGlow = (function () {

    const cv = document.createElement('canvas');

    cv.width = cv.height = HALO_R;

    const c2 = cv.getContext('2d');

    const g = c2.createRadialGradient(HALO_R / 2, HALO_R / 2, 0, HALO_R / 2, HALO_R / 2, HALO_R / 2);

    g.addColorStop(0, 'rgba(120,225,255,0.55)');

    g.addColorStop(1, 'rgba(120,225,255,0)');

    c2.fillStyle = g;

    c2.fillRect(0, 0, HALO_R, HALO_R);

    return cv;

  })();



  // ---- galactic band ------------------------------------------------

  // Direction-only: no wrap and no parallax, so it behaves like real

  // infinity and can never pop into view.

  const SKY_R = 13000;

  const GAL_N = norm([0.45, 0.72, 0.53]);      // galactic plane normal

  const GAL_U = norm(cross(GAL_N, [0, 0, 1]));

  const GAL_V = norm(cross(GAL_N, GAL_U));

  const skyNoise = makeNoise(4242);



  function bandDir(a, off) {

    const ca = Math.cos(a), sa = Math.sin(a);

    return norm([

      GAL_U[0] * ca + GAL_V[0] * sa + GAL_N[0] * off,

      GAL_U[1] * ca + GAL_V[1] * sa + GAL_N[1] * off,

      GAL_U[2] * ca + GAL_V[2] * sa + GAL_N[2] * off

    ]);

  }



  const bandBlobs = [];

  const bandStars = [];

  {

    const N = 420;

    for (let i = 0; i < N; i++) {

      const a = i / N * TAU, ca = Math.cos(a), sa = Math.sin(a);

      const b = skyNoise.fbm(ca * 2.4 + 11, sa * 2.4 + 5, 4);

      const dust = skyNoise.fbm(ca * 5.5 + 47, sa * 5.5 + 19, 3);

      const off = (skyNoise.noise(ca * 4.3, sa * 4.3) - 0.5) * 0.26;

      // fbm brightness minus dark dust lanes where the noise dips

      const bright = Math.max(0, b * 1.5 - (dust < 0.44 ? (0.44 - dust) * 2.8 : 0));

      if (bright < 0.04) continue;

      bandBlobs.push({

        dir: bandDir(a, off),

        r: 1500 + b * 3400,

        a: Math.min(0.17, bright * 0.13),

        tex: b > 0.58 ? softWarm : softCool

      });

    }

    for (let i = 0; i < 2600; i++) {

      const a = Math.random() * TAU;

      const g = (Math.random() + Math.random() + Math.random() - 1.5) * 0.3; // hug the plane

      bandStars.push({

        dir: bandDir(a, g),

        s: Math.random() < 0.1 ? 2 : 1,

        b: (Math.random() * 3) | 0,

        c: (Math.random() * 3) | 0

      });

    }

  }



  // ---- galactic filaments (cosmic web strands) ----------------------

  const FIELD_FIL = FIELD * 4;

  const FIL_COUNT = 26;

  const filPalette = [

    [120, 170, 255], [160, 200, 255], [140, 235, 220], [255, 200, 160], [200, 160, 255]

  ];



  function catmullRom(points, per) {

    const out = [], n = points.length;

    for (let i = 0; i < n - 1; i++) {

      const p0 = points[Math.max(0, i - 1)], p1 = points[i];

      const p2 = points[i + 1], p3 = points[Math.min(n - 1, i + 2)];

      for (let s = 0; s < per; s++) {

        const t = s / per, t2 = t * t, t3 = t2 * t;

        out.push([

          0.5 * (2 * p1[0] + (-p0[0] + p2[0]) * t + (2 * p0[0] - 5 * p1[0] + 4 * p2[0] - p3[0]) * t2 + (-p0[0] + 3 * p1[0] - 3 * p2[0] + p3[0]) * t3),

          0.5 * (2 * p1[1] + (-p0[1] + p2[1]) * t + (2 * p0[1] - 5 * p1[1] + 4 * p2[1] - p3[1]) * t2 + (-p0[1] + 3 * p1[1] - 3 * p2[1] + p3[1]) * t3),

          0.5 * (2 * p1[2] + (-p0[2] + p2[2]) * t + (2 * p0[2] - 5 * p1[2] + 4 * p2[2] - p3[2]) * t2 + (-p0[2] + 3 * p1[2] - 3 * p2[2] + p3[2]) * t3)

        ]);

      }

    }

    out.push(points[n - 1].slice());

    return out;

  }



  function makeFilament() {

    const seed = (Math.random() * 9999) | 0;

    const nz = makeNoise(seed);

    const n = 5 + ((Math.random() * 5) | 0);

    let dir = norm([Math.random() * 2 - 1, (Math.random() * 2 - 1) * 0.55, Math.random() * 2 - 1]);

    let x = (Math.random() * 2 - 1) * FIELD_FIL * 0.8;

    let y = (Math.random() * 2 - 1) * FIELD_FIL * 0.5;

    let z = (Math.random() * 2 - 1) * FIELD_FIL * 0.8;

    const step = 500 + Math.random() * 600;

    const nodes = [];

    for (let i = 0; i < n; i++) {

      nodes.push([x, y, z]);

      const w1 = nz.noise(i * 1.7, seed * 0.01) - 0.5;

      const w2 = nz.noise(seed * 0.02, i * 2.3) - 0.5;

      dir = norm([dir[0] + w1 * 0.9, dir[1] + w2 * 0.5, dir[2] + w1 * 0.4]);

      x += dir[0] * step; y += dir[1] * step; z += dir[2] * step;

    }

    // faint star clusters gathered at the knots, in local offsets

    const knots = [];

    for (let i = 0; i < n; i++) {

      const k = [];

      const m = 9 + ((Math.random() * 10) | 0);

      for (let j = 0; j < m; j++) {

        k.push([(Math.random() * 2 - 1) * 150, (Math.random() * 2 - 1) * 150, (Math.random() * 2 - 1) * 150]);

      }

      knots.push(k);

    }

    const pts = catmullRom(nodes, 7);

    // Bounding sphere, so drawFilaments can reject a whole strand with one

    // distance test instead of projecting its 35 points. Headroom covers the

    // stroke width and the 150-unit knot star offsets. Translation by f.off

    // moves the sphere with the strand.

    let bx = 0, by = 0, bz = 0;

    for (const p of pts) { bx += p[0]; by += p[1]; bz += p[2]; }

    bx /= pts.length; by /= pts.length; bz /= pts.length;

    let br = 0;

    for (const p of pts) {

      const l = Math.sqrt((p[0] - bx) * (p[0] - bx) + (p[1] - by) * (p[1] - by) + (p[2] - bz) * (p[2] - bz));

      if (l > br) br = l;

    }

    return {

      nodes, knots, pts,

      center: [bx, by, bz], radius: br + 200,

      ci: (Math.random() * filPalette.length) | 0,

      colorStr: '',

      w: 22 + Math.random() * 46,

      glow: 0.45 + Math.random() * 0.55,

      off: [0, 0, 0]

    };

  }

  const filaments = [];

  for (let i = 0; i < FIL_COUNT; i++) {

    const f = makeFilament();

    f.colorStr = filPalette[f.ci][0] + ',' + filPalette[f.ci][1] + ',' + filPalette[f.ci][2]; // once, not per frame

    filaments.push(f);

  }



  // Filaments live far away: they fade out before they reach the camera and

  // before a wrap can land them, so they never pop and never straddle you.

  function filFade(d) {

    if (d < 700 || d > FIELD_FIL) return 0;

    return smoothstep(Math.min(1, (d - 700) / 1300)) * smoothstep(Math.min(1, (FIELD_FIL - d) / 2600));

  }



  // ---- spiral galaxies ----------------------------------------------

  const FIELD_GAL = FIELD * 2.4;

  const GALAXY_COUNT = 12;

  const galPalette = [[150, 190, 255], [255, 200, 170], [170, 240, 225], [215, 175, 255]];



  function makeGalaxyTexture(seed, col) {

    const S = 160, R = S / 2;

    const cv = document.createElement('canvas');

    cv.width = cv.height = S;

    const c2 = cv.getContext('2d');

    const nz = makeNoise(seed);

    const cs = col[0] + ',' + col[1] + ',' + col[2];

    c2.globalCompositeOperation = 'lighter';

    const g0 = c2.createRadialGradient(R, R, 0, R, R, R);

    g0.addColorStop(0, 'rgba(255,248,235,0.7)');

    g0.addColorStop(0.16, 'rgba(' + cs + ',0.32)');

    g0.addColorStop(0.52, 'rgba(' + cs + ',0.1)');

    g0.addColorStop(1, 'rgba(' + cs + ',0)');

    c2.fillStyle = g0;

    c2.fillRect(0, 0, S, S);

    const arms = 2 + (seed % 2);

    const twist = 2.6 + nz.noise(seed, 3) * 1.9;

    for (let arm = 0; arm < arms; arm++) {

      const base = arm * TAU / arms + nz.noise(arm * 2.1, seed) * 1.2;

      const steps = 110;

      for (let i = 1; i < steps; i++) {

        const t = i / steps;

        const rr = 8 + t * R * 0.92;

        const th = base + t * twist + (nz.noise(i * 0.19, arm * 3.7) - 0.5) * 0.7;

        const jit = (nz.noise(i * 0.63, arm * 1.9) - 0.5) * 14 * t;

        const x = R + Math.cos(th) * (rr + jit);

        const y = R + Math.sin(th) * (rr + jit) * 0.58; // tilted disc

        const rad = 4 + t * 9;

        const a = (1 - t * 0.6) * 0.17;

        const gg = c2.createRadialGradient(x, y, 0, x, y, rad);

        gg.addColorStop(0, 'rgba(' + cs + ',' + a.toFixed(3) + ')');

        gg.addColorStop(1, 'rgba(' + cs + ',0)');

        c2.fillStyle = gg;

        c2.beginPath(); c2.arc(x, y, rad, 0, TAU); c2.fill();

        if (nz.noise(i * 1.31, arm * 7.7) > 0.86) { // young blue star knots

          c2.fillStyle = 'rgba(200,230,255,' + (0.3 + nz.noise(i, arm) * 0.4).toFixed(2) + ')';

          c2.beginPath(); c2.arc(x, y, 1.3, 0, TAU); c2.fill();

        }

      }

    }

    c2.globalCompositeOperation = 'destination-out';

    for (let k = 0; k < 26; k++) { // dark dust lanes cutting the disc

      const t = nz.noise(k * 2.7, seed);

      const th = nz.noise(k * 1.1, seed * 0.3) * TAU;

      const rr = 12 + t * R * 0.85;

      const x = R + Math.cos(th) * rr, y = R + Math.sin(th) * rr * 0.58;

      const rad = 9 + t * 12;

      const gg = c2.createRadialGradient(x, y, 0, x, y, rad);

      gg.addColorStop(0, 'rgba(0,0,0,0.75)');

      gg.addColorStop(1, 'rgba(0,0,0,0)');

      c2.fillStyle = gg;

      c2.beginPath(); c2.arc(x, y, rad, 0, TAU); c2.fill();

    }

    c2.globalCompositeOperation = 'source-over';

    return cv;

  }

  const galaxyTex = galPalette.map((c, i) => makeGalaxyTexture(511 + i * 53, c));



  function makeGalaxy() {

    return {

      x: (Math.random() * 2 - 1) * FIELD_GAL,

      y: (Math.random() * 2 - 1) * FIELD_GAL * 0.55,

      z: (Math.random() * 2 - 1) * FIELD_GAL,

      r: 380 + Math.random() * 720,

      ci: (Math.random() * galaxyTex.length) | 0,

      rot: Math.random() * TAU,

      squash: 0.4 + Math.random() * 0.6

    };

  }

  const galaxies = [];

  for (let i = 0; i < GALAXY_COUNT; i++) galaxies.push(makeGalaxy());



  // ---- sunlit planets -----------------------------------------------

  const FIELD_PLANET = FIELD * 2.2;

  const PLANET_COUNT = 8;

  const planetPal = [

    [[36, 64, 118], [58, 104, 146], [214, 228, 238]],  // ocean

    [[92, 66, 48], [132, 104, 72], [226, 216, 200]],   // rocky

    [[48, 82, 70], [108, 140, 96], [228, 236, 224]],   // verdant

    [[124, 86, 58], [176, 126, 84], [242, 222, 192]],  // desert

    [[40, 52, 82], [92, 112, 152], [222, 232, 246]]    // ice

  ];



  function makePlanetTexture(seed) {

    const S = 128;

    const cv = document.createElement('canvas');

    cv.width = cv.height = S;

    const c2 = cv.getContext('2d');

    const img = c2.createImageData(S, S), data = img.data;

    const nz = makeNoise(seed);

    const pal = planetPal[seed % planetPal.length];

    for (let py = 0; py < S; py++) {

      for (let px = 0; px < S; px++) {

        const dx = (px - S / 2 + 0.5) / (S / 2), dy = (py - S / 2 + 0.5) / (S / 2);

        const rr = dx * dx + dy * dy;

        const i = (py * S + px) * 4;

        if (rr >= 1) { data[i + 3] = 0; continue; }

        data[i + 3] = 255;

        const z = Math.sqrt(1 - rr);

        const lon = Math.atan2(dy, dx) + seed * 0.37;

        const lat = Math.asin(clamp(z, -1, 1)) - Math.PI / 2;

        const cl = Math.cos(lat);

        // seamless-in-longitude continent field

        const c = nz.fbm(Math.cos(lon) * 2.1 + 7, Math.sin(lon) * 2.1 + 3 + lat * 2.6, 4);

        const land = c > 0.52;

        let base = land ? pal[1] : pal[0];

        if (land) {

          const h = Math.min(1, (c - 0.52) * 3.2);

          base = [base[0] + (pal[2][0] - base[0]) * h * 0.45,

                  base[1] + (pal[2][1] - base[1]) * h * 0.45,

                  base[2] + (pal[2][2] - base[2]) * h * 0.45];

        }

        // ice caps

        const ice = Math.abs(lat) > 1.18 + nz.noise(lon * 3, 9) * 0.3;

        if (ice) {

          const k = Math.min(1, (Math.abs(lat) - 1.1) * 3);

          base = [base[0] + (240 - base[0]) * k, base[1] + (246 - base[1]) * k, base[2] + (252 - base[2]) * k];

        }

        // cloud banding

        const cloud = nz.fbm(Math.cos(lon) * 3.3 + 21, Math.sin(lon) * 3.3 + 17 + lat * 3.4, 3);

        const ca = clamp((cloud - 0.52) * 2.4, 0, 1) * 0.72;

        data[i]     = base[0] + (250 - base[0]) * ca;

        data[i + 1] = base[1] + (252 - base[1]) * ca;

        data[i + 2] = base[2] + (255 - base[2]) * ca;

        // limb darkening so the sprite reads as a sphere even before shading

        const limb = 0.72 + 0.28 * Math.pow(z, 0.45);

        data[i] *= limb; data[i + 1] *= limb; data[i + 2] *= limb;

      }

    }

    c2.putImageData(img, 0, 0);

    return cv;

  }

  const planetTex = [];

  for (let i = 0; i < 5; i++) planetTex.push(makePlanetTexture(101 + i * 37));



  function makePlanet() {

    const nrm = norm([Math.random() * 2 - 1, Math.random() * 1.2 + 0.4, Math.random() * 2 - 1]);

    let A = cross(nrm, [0, 1, 0]);

    if (len(A) < 1e-4) A = [1, 0, 0]; else A = norm(A);

    const B = norm(cross(nrm, A));

    const ringed = Math.random() < 0.4;

    return {

      x: (Math.random() * 2 - 1) * FIELD_PLANET * 0.9,

      y: (Math.random() * 2 - 1) * FIELD_PLANET * 0.5,

      z: (Math.random() * 2 - 1) * FIELD_PLANET * 0.9,

      r: 240 + Math.random() * 620,

      tex: (Math.random() * planetTex.length) | 0,

      spin: Math.random() * TAU,

      spinRate: (Math.random() - 0.5) * 0.06,

      atmo: [[120, 190, 255], [255, 170, 120], [150, 240, 210], [205, 205, 255]][(Math.random() * 4) | 0],

      atmoStr: '',

      ring: ringed,

      ringA: A, ringB: B,

      ringR: 1.7 + Math.random() * 0.9,

      ringW: 26 + Math.random() * 40

    };

  }

  const planets = [];

  for (let i = 0; i < PLANET_COUNT; i++) {

    const pl = makePlanet();

    pl.atmoStr = pl.atmo[0] + ',' + pl.atmo[1] + ',' + pl.atmo[2]; // built once, not per frame

    planets.push(pl);

  }



  // ---- meteors / shooting stars -------------------------------------

  const meteors = [];

  let nextMeteor = 0, exhaustTick = 0;

  const exhaust = [];



  function spawnMeteors(cam, now) {

    if (now < nextMeteor) return;

    nextMeteor = now + 500 + Math.random() * 2200;

    const burst = Math.random() < 0.22 ? 2 + ((Math.random() * 3) | 0) : 1;

    for (let i = 0; i < burst && meteors.length < 16; i++) {

      // spawn in the forward hemisphere, off-axis

      const d = norm([(Math.random() * 2 - 1) * 1.1, (Math.random() * 2 - 1) * 0.8, 0.45 + Math.random() * 0.55]);

      const dist = 500 + Math.random() * 900;

      // travel across the view so it reads as a streak

      let lat = cross(d, [0, 1, 0]);

      if (len(lat) < 1e-4) lat = [1, 0, 0]; else lat = norm(lat);

      lat = rotateAbout(lat, d, Math.random() * TAU);

      const speed = 700 + Math.random() * 1500;

      const fireball = Math.random() < 0.14;

      const vx = lat[0] * speed + d[0] * (Math.random() * 220 - 80);

      const vy = lat[1] * speed + d[1] * (Math.random() * 220 - 80);

      const vz = lat[2] * speed + d[2] * (Math.random() * 220 - 80);

      meteors.push({

        x: cam.camPos[0] + d[0] * dist + (Math.random() - 0.5) * 300,

        y: cam.camPos[1] + d[1] * dist + (Math.random() - 0.5) * 300,

        z: cam.camPos[2] + d[2] * dist + (Math.random() - 0.5) * 300,

        vx: vx, vy: vy, vz: vz,

        life: 0, max: 0.9 + Math.random() * 1.2,

        trail: (fireball ? 0.22 : 0.12) + Math.random() * 0.06,

        w: fireball ? 3.2 + Math.random() * 2 : 1.2 + Math.random() * 1.4,

        warm: fireball || Math.random() < 0.3,

        fireball: fireball

      });

    }

  }



  // ---- near-field dust motes (speed cue) ----------------------------

  const DUST_COUNT = 460, DUST_R = 620;

  const dust = [];

  for (let i = 0; i < DUST_COUNT; i++) {

    dust.push({

      x: (Math.random() * 2 - 1) * DUST_R,

      y: (Math.random() * 2 - 1) * DUST_R,

      z: (Math.random() * 2 - 1) * DUST_R

    });

  }



  // ------------------------------------------------------------------

  // Camera: chase cam behind the ship with a FIXED WORLD-UP view.

  // The camera's up vector is always (0,1,0), so the horizon stays level

  // and the view never rolls or flips no matter how the ship yaws or

  // pitches. Position and look-target are exponentially smoothed (no

  // overshoot, no drift) so turns feel fluid.

  //

  // The view direction follows the FLIGHT PATH, not the nose. The nose can

  // swing at ~34 deg/s, but the ship's course only changes as its velocity

  // is rebuilt along the new nose. So during a turn the sky holds still and

  // the ship rotates inside the frame, instead of the whole world spinning

  // the other way under the turn. Once you are flying straight, velocity and

  // nose agree and the camera behaves exactly as it always did.

  //

  //   CAM_VIEW_BLEND   0 = old behaviour (view snaps to the nose).

  //                    higher = steadier sky, ship swings more in frame.

  //   CAM_VIEW_FOLLOW  how fast the view settles. Lower = steeper lag.

  //   CAM_MAX_ANGLE    how far the view may fall behind the nose, so the

  //                    ship can never swing out of frame.

  // ------------------------------------------------------------------

  const CAM_BACK = 110;         // distance behind the ship

  const CAM_UP = 55;            // height above the ship

  const CAM_FOLLOW = 7;         // smoothing rate (1/s) — softer chase

  const CAM_LOOKAHEAD = 26;     // camera aims along the view, ship leads it

  const CAM_VIEW_BLEND = 0.8;   // nose vs. flight path, 0 = pure nose

  const CAM_VIEW_FOLLOW = 0.6;  // view settling rate (1/s)

  const CAM_MAX_ANGLE = 0.8;    // rad (~46 deg) soft limit on nose-vs-view lag

  const CAM_UNWIND = 0.9;       // rad/s — how gently the lag is pulled back

  let camState = null;



  function cameraBasis(dt) {

    const fwd = ship.fwd;



    // What the view is allowed to turn toward. Blended with the nose so a

    // ship that is barely moving (or decelerating out of the old direction)

    // still has a well-defined view.

    let want = fwd;

    if (CAM_VIEW_BLEND > 0) {

      const sp = len(ship.vel);

      if (sp > 1) {

        const w = CAM_VIEW_BLEND;

        const bx = fwd[0] * (1 - w) + (ship.vel[0] / sp) * w;

        const by = fwd[1] * (1 - w) + (ship.vel[1] / sp) * w;

        const bz = fwd[2] * (1 - w) + (ship.vel[2] / sp) * w;

        const bl = Math.hypot(bx, by, bz);

        if (bl > 1e-6) want = [bx / bl, by / bl, bz / bl];

      }

    }



    const first = !camState;

    if (first) camState = { pos: [0, 0, 0], tgt: [0, 0, 0], view: want.slice() };



    const kv = 1 - Math.exp(-CAM_VIEW_FOLLOW * dt);

    for (let i = 0; i < 3; i++) camState.view[i] += (want[i] - camState.view[i]) * kv;



    // Soft limit on how far the view may fall behind the nose. A hard cap

    // would snap the view in spikes, which is the very thing being reduced.

    const ca = clamp(dot3(camState.view, fwd), -1, 1);

    const lag = Math.acos(ca);

    if (lag > CAM_MAX_ANGLE) {

      const ax = cross(camState.view, fwd);

      const al = len(ax);

      if (al > 1e-6) {

        const n = [ax[0] / al, ax[1] / al, ax[2] / al];

        // positive rotation about cross(view, nose) swings the view back

        // toward the nose, but only by what this frame can afford

        const r = rotateAbout(camState.view, n, Math.min(lag - CAM_MAX_ANGLE, CAM_UNWIND * dt));

        camState.view[0] = r[0]; camState.view[1] = r[1]; camState.view[2] = r[2];

      }

    }



    const view = camState.view;

    const desiredPos = [

      ship.pos[0] - view[0] * CAM_BACK,

      ship.pos[1] - view[1] * CAM_BACK + CAM_UP,

      ship.pos[2] - view[2] * CAM_BACK

    ];

    const desiredTgt = [

      ship.pos[0] + view[0] * CAM_LOOKAHEAD,

      ship.pos[1] + view[1] * CAM_LOOKAHEAD + 8,

      ship.pos[2] + view[2] * CAM_LOOKAHEAD

    ];

    const k = first ? 1 : 1 - Math.exp(-CAM_FOLLOW * dt);

    for (let i = 0; i < 3; i++) {

      camState.pos[i] += (desiredPos[i] - camState.pos[i]) * k;

      camState.tgt[i] += (desiredTgt[i] - camState.tgt[i]) * k;

    }

    const forward = norm(sub(camState.tgt, camState.pos));

    let xAxis = cross(forward, [0, 1, 0]); // screen right

    if (len(xAxis) < 1e-6) xAxis = [1, 0, 0]; else xAxis = norm(xAxis);

    const yAxis = cross(xAxis, forward);   // screen up (always world-level)

    lastCam = { camPos: camState.pos, xAxis, yAxis, zAxis: forward };

    return lastCam;

  }



  // Transform a world point into camera space and project it into `out`, a

  // pooled object, so the render loop allocates nothing. Returns null if behind.

  function project(px, py, pz, cam, out) {

    const dx = px - cam.camPos[0];

    const dy = py - cam.camPos[1];

    const dz = pz - cam.camPos[2];

    const cz = dx * cam.zAxis[0] + dy * cam.zAxis[1] + dz * cam.zAxis[2];

    if (cz <= 0.5) return null;   // depth first: most rejects stop here

    out.x = CX + ((dx * cam.xAxis[0] + dy * cam.xAxis[1] + dz * cam.xAxis[2]) / cz) * FOCAL;

    out.y = CY - ((dx * cam.yAxis[0] + dy * cam.yAxis[1] + dz * cam.yAxis[2]) / cz) * FOCAL;

    out.z = cz;

    return out;

  }



  // ------------------------------------------------------------------

  // Ship geometry (local space, nose toward -Z, scale factor 15)

  // ------------------------------------------------------------------

  const SHIP_SCALE = 15;

  const shipVerts = [

    [0, 0, -1.4],        // 0  nose tip

    [-0.5, 0.15, -0.4],  // 1  cockpit ring left

    [0.5, 0.15, -0.4],   // 2  cockpit ring right

    [0, 0.42, -0.4],     // 3  cockpit ring top

    [-0.62, 0, 0.6],     // 4  mid fuselage left

    [0.62, 0, 0.6],      // 5  mid fuselage right

    [0, 0.5, 0.6],       // 6  mid fuselage top

    [-0.5, 0, 1.3],      // 7  rear left

    [0.5, 0, 1.3],       // 8  rear right

    [0, 0.4, 1.3],       // 9  rear top

    [-2.1, 0.05, 0.9],   // 10 left wing tip (swept back)

    [2.1, 0.05, 0.9],    // 11 right wing tip (swept back)

    [-0.62, 0, 1.25],    // 12 left wing root rear

    [0.62, 0, 1.25],     // 13 right wing root rear

    [0, 1.15, 1.55],     // 14 tail fin tip

    [-0.3, 0.35, 1.25],  // 15 tail fin base left

    [0.3, 0.35, 1.25],   // 16 tail fin base right

    [-1.0, 0.55, 1.6],   // 17 left side fin tip

    [1.0, 0.55, 1.6]     // 18 right side fin tip

  ];



  // [a,b,c] index triples, plus a color key: h=hull, w=wing, g=glass, e=engine

  const shipFaces = [

    // nose cone

    [0, 1, 2, 'h'],

    [0, 2, 3, 'h'],

    [0, 3, 1, 'h'],

    // glowing cockpit window

    [1, 3, 2, 'g'],

    // upper fuselage

    [1, 3, 6, 'h'],

    [1, 6, 4, 'h'],

    [2, 5, 6, 'h'],

    [2, 6, 3, 'h'],

    // lower fuselage

    [4, 6, 5, 'h'],

    [4, 5, 8, 'h'],

    [4, 8, 7, 'h'],

    // rear engine block

    [7, 8, 9, 'e'],

    [7, 9, 5, 'h'],

    [8, 5, 9, 'h'],

    // left swept wing

    [4, 10, 12, 'w'],

    [4, 12, 7, 'w'],

    [6, 4, 10, 'w'],

    // right swept wing

    [5, 11, 13, 'w'],

    [5, 13, 8, 'w'],

    [6, 5, 11, 'w'],

    // tail fin

    [15, 16, 14, 'h'],

    [9, 14, 15, 'h'],

    [9, 16, 14, 'h'],

    // side tail fins

    [7, 17, 12, 'w'],

    [8, 13, 18, 'w']

  ];



  const shipColors = {

    h: [74, 80, 96],   // dark gray hull

    w: [104, 112, 132], // lighter wing

    g: [130, 226, 255], // glowing blue cockpit

    e: [40, 44, 58]    // engine block

  };



  // ------------------------------------------------------------------

  // Update

  // ------------------------------------------------------------------

  let distance = 0;

  let last = performance.now();



  function update(dt) {

    // --- steering: one smooth arc, eased in and eased out -------------

    let errTrue = 0;

    if (hasTarget) {

      errTrue = Math.acos(clamp(dot3(ship.fwd, targetFwd), -1, 1));



      // Route: take the direct great circle, unless that arc would pitch the

      // nose past its authority — then level out toward the target's bearing

      // first and change pitch afterwards. That is what a real ship does, and

      // it is what stops a 180-degree reversal from stalling against the

      // pitch limit.

      let tgt = targetFwd;

      const a0 = cross(ship.fwd, targetFwd);

      const a0l = len(a0);

      if (a0l > 1e-4) {

        const nx = a0[0] / a0l, ny = a0[1] / a0l, nz = a0[2] / a0l;

        const err0 = Math.acos(clamp(dot3(ship.fwd, targetFwd), -1, 1));

        // Along the arc, nose.y(t) = nose.y*cos t + cy*sin t where

        // cy = (axis x nose).y. Its peak inside the swept range is what

        // matters — not the peak of the whole great circle.

        const cy = nz * ship.fwd[0] - nx * ship.fwd[2];

        const fy = ship.fwd[1];

        let hi = Math.max(fy, fy * Math.cos(err0) + cy * Math.sin(err0));

        let lo = Math.min(fy, fy * Math.cos(err0) + cy * Math.sin(err0));

        const tp = Math.atan2(cy, fy);

        if (tp > 0 && tp < err0) hi = Math.max(hi, Math.hypot(fy, cy));

        const tn = tp - Math.PI;

        if (tn > 0 && tn < err0) lo = Math.min(lo, -Math.hypot(fy, cy));

        if ((hi > PITCH_SIN || lo < -PITCH_SIN) && Math.hypot(targetFwd[0], targetFwd[2]) > 1e-3) {

          const hh = Math.hypot(targetFwd[0], targetFwd[2]);

          tgt = [targetFwd[0] / hh, 0, targetFwd[2] / hh];

        }

      }



      const err = Math.acos(clamp(dot3(ship.fwd, tgt), -1, 1));

      if (err > 1e-4) {

        if (err > Math.PI - 0.02) {

          // pointing exactly backwards: the cross product is undefined, so

          // pick the natural rotation — yaw level about world up

          const ax = cross(ship.fwd, [0, 1, 0]);

          if (len(ax) > 1e-4) { turnAxis[0] = ax[0] / len(ax); turnAxis[1] = ax[1] / len(ax); turnAxis[2] = ax[2] / len(ax); }

          else { turnAxis[0] = 1; turnAxis[1] = 0; turnAxis[2] = 0; }

        } else if (err > 0.05) {

          // recompute while the arc is well defined; below that the cross

          // product of two near-parallel vectors is noise, and re-deriving it

          // per frame makes the nose jitter. Remembering the axis instead lets

          // the turn settle dead straight — the stored axis is perpendicular to

          // both directions, so rotating by the remaining error lands exactly

          // on the target.

          const ax = cross(ship.fwd, tgt);

          const al = len(ax) || 1;

          turnAxis[0] = ax[0] / al; turnAxis[1] = ax[1] / al; turnAxis[2] = ax[2] / al;

        }

        const axis = turnAxis;

        const cur = len(ship.omega);

        const want = Math.min(TURN_MAX, err * TURN_GAIN);

        const rate = Math.max(0, cur + clamp(want - cur, -TURN_SLEW * dt, TURN_SLEW * dt));

        const step = Math.min(rate * dt, err); // never swings past the target

        ship.fwd = rotateAbout(ship.fwd, axis, step);

        ship.omega[0] = axis[0] * rate;

        ship.omega[1] = axis[1] * rate;

        ship.omega[2] = axis[2] * rate;

      } else {

        ship.omega[0] = ship.omega[1] = ship.omega[2] = 0;

      }

      // safety net: keep the nose off vertical so the level camera stays conditioned

      if (Math.abs(ship.fwd[1]) > PITCH_SIN) {

        const y = clamp(ship.fwd[1], -PITCH_SIN, PITCH_SIN);

        const hh = Math.hypot(ship.fwd[0], ship.fwd[2]) || 1e-6;

        const k = Math.sqrt(Math.max(0, 1 - y * y)) / hh;

        ship.fwd[0] *= k; ship.fwd[1] = y; ship.fwd[2] *= k;

      }

    }



    // heading / pitch are just the nose vector read back out

    ship.pitch = Math.asin(clamp(ship.fwd[1], -1, 1));

    ship.heading = Math.atan2(ship.fwd[0], -ship.fwd[2]);



    // Bank into the turn (visual roll only — the camera itself stays level).

    // Heading grows when the ship rotates about -Y, so the yaw rate is -omega[1].

    const targetBank = clamp(-ship.omega[1] * 0.95, -0.62, 0.62);

    ship.bank += (targetBank - ship.bank) * Math.min(1, dt * 2.6);



    // Throttle eases up once the nose is on course and stays low while the

    // ship is still swinging through the turn, so the burn matches the aim.

    const wantThrottle = hasTarget ? 0.35 + 0.65 * (1 - Math.min(1, errTrue / 1.15)) : 0;

    ship.throttle += (wantThrottle - ship.throttle) * Math.min(1, dt * THROTTLE_RATE);



    // Thrust along the nose direction

    const fwd = ship.fwd;

    if (ship.throttle > 0.001) {

      const a = ACCEL * ship.throttle * dt;

      ship.vel[0] += fwd[0] * a;

      ship.vel[1] += fwd[1] * a;

      ship.vel[2] += fwd[2] * a;

    }



    // integrate velocity with drag

    const dragF = Math.exp(-DRAG * dt);

    ship.vel[0] *= dragF;

    ship.vel[1] *= dragF;

    ship.vel[2] *= dragF;



    // clamp speed

    const sp = len(ship.vel);

    if (sp > MAX_SPEED) {

      const k = MAX_SPEED / sp;

      ship.vel[0] *= k; ship.vel[1] *= k; ship.vel[2] *= k;

    }



    // integrate position

    ship.pos[0] += ship.vel[0] * dt;

    ship.pos[1] += ship.vel[1] * dt;

    ship.pos[2] += ship.vel[2] * dt;

    distance += sp * dt;



    // Spin asteroids, planets

    for (const a of asteroids) {

      a.rot[0] += a.spin[0] * dt;

      a.rot[1] += a.spin[1] * dt;

      a.rot[2] += a.spin[2] * dt;

    }

    for (const pl of planets) pl.spin += pl.spinRate * dt;



    // Engine exhaust: soft particles shed from the nozzles, drifting back

    if (ship.throttle > 0.12) {

      for (let i = 0; i < 2; i++) {

        const e = ENGINE_LOCAL[exhaustTick++ & 1];

        const wp = shipWorldPoint(e, SHIP_W);

        const back = 150 + Math.random() * 190;

        exhaust.push({

          x: wp[0], y: wp[1], z: wp[2],

          vx: ship.vel[0] * 0.4 - fwd[0] * back + (Math.random() - 0.5) * 45,

          vy: ship.vel[1] * 0.4 - fwd[1] * back + (Math.random() - 0.5) * 45,

          vz: ship.vel[2] * 0.4 - fwd[2] * back + (Math.random() - 0.5) * 45,

          life: 0, max: 0.5 + Math.random() * 0.5, r: 0.6 + Math.random() * 1.1

        });

      }

      if (exhaust.length > 240) exhaust.splice(0, exhaust.length - 240);

    }

    for (let i = exhaust.length - 1; i >= 0; i--) {

      const p = exhaust[i];

      p.life += dt;

      if (p.life >= p.max) { exhaust.splice(i, 1); continue; }

      p.x += p.vx * dt; p.y += p.vy * dt; p.z += p.vz * dt;

      p.vx *= 0.985; p.vy *= 0.985; p.vz *= 0.985;

    }



    // Meteors

    for (let i = meteors.length - 1; i >= 0; i--) {

      const m = meteors[i];

      m.life += dt;

      if (m.life >= m.max) { meteors.splice(i, 1); continue; }

      m.x += m.vx * dt; m.y += m.vy * dt; m.z += m.vz * dt;

    }

  }



  // ------------------------------------------------------------------

  // Rendering

  // ------------------------------------------------------------------

  function drawBackground() {

    if (bgLayer) {

      ctx.drawImage(bgLayer, 0, 0, W, H);

    } else {

      ctx.fillStyle = '#050510';

      ctx.fillRect(0, 0, W, H);

    }

  }



  function drawStars(cam) {

    // Batch stars into 4 color paths for fast rendering

    const paths = [new Path2D(), new Path2D(), new Path2D(), new Path2D()];

    const sx = ship.pos[0], sy = ship.pos[1], sz = ship.pos[2];

    const xlo = sx - FIELD, xhi = sx + FIELD, ylo = sy - FIELD, yhi = sy + FIELD, zlo = sz - FIELD, zhi = sz + FIELD;

    const cp = cam.camPos, xa = cam.xAxis, ya = cam.yAxis, za = cam.zAxis;

    for (let i = 0; i < stars.length; i++) {

      const st = stars[i];

      // infinite space: wrap around the ship so stars respawn ahead

      if (st.x < xlo) st.x += 2 * FIELD; else if (st.x > xhi) st.x -= 2 * FIELD;

      if (st.y < ylo) st.y += 2 * FIELD; else if (st.y > yhi) st.y -= 2 * FIELD;

      if (st.z < zlo) st.z += 2 * FIELD; else if (st.z > zhi) st.z -= 2 * FIELD;

      const dx = st.x - cp[0], dy = st.y - cp[1], dz = st.z - cp[2];

      const cz = dx * za[0] + dy * za[1] + dz * za[2];

      if (cz <= 0.5) continue;

      const px = CX + ((dx * xa[0] + dy * xa[1] + dz * xa[2]) / cz) * FOCAL;

      if (px < -4 || px > W + 4) continue;

      const py = CY - ((dx * ya[0] + dy * ya[1] + dz * ya[2]) / cz) * FOCAL;

      if (py < -4 || py > H + 4) continue;

      paths[st.ci].rect(px, py, st.s, st.s);

    }

    for (let i = 0; i < 4; i++) {

      ctx.fillStyle = starStyle[i];

      ctx.fill(paths[i]);

    }

  }



  function drawNebulae(cam) {

    // Nebulae wrap in a box of +/-FIELD_NEB (2x the ship field) around the

    // ship: the furthest one can ever be is the box corner (NEB_MAX, ~9006u).

    // A wrap teleports a nebula to somewhere between FIELD_NEB (one axis) and

    // NEB_MAX (a corner) away, so alpha is a pure function of distance:

    // exactly 0 everywhere a wrap can land, ramping to full at a FIELD in.

    const NEB_MAX = FIELD_NEB * Math.sqrt(3); // view/cull distance, 2x the old one

    // painter's: far first

    list.length = 0;

    for (const n of nebulae) {

      // infinite space: wrap around the ship

      if (n.x < ship.pos[0] - FIELD_NEB) n.x += 2 * FIELD_NEB; else if (n.x > ship.pos[0] + FIELD_NEB) n.x -= 2 * FIELD_NEB;

      if (n.y < ship.pos[1] - FIELD_NEB) n.y += 2 * FIELD_NEB; else if (n.y > ship.pos[1] + FIELD_NEB) n.y -= 2 * FIELD_NEB;

      if (n.z < ship.pos[2] - FIELD_NEB) n.z += 2 * FIELD_NEB; else if (n.z > ship.pos[2] + FIELD_NEB) n.z -= 2 * FIELD_NEB;

      const dz = n.z - cam.camPos[2];

      const dx = n.x - cam.camPos[0];

      const dy = n.y - cam.camPos[1];

      const dist = Math.sqrt(dx * dx + dy * dy + dz * dz);

      if (dist > NEB_MAX) continue;

      const p = project(n.x, n.y, n.z, cam, P_ONE);

      if (!p) continue;

      const e = ENTRY[list.length];

      e.it = n; e.x = p.x; e.y = p.y; e.z = p.z; e.dist = dist; e.fade = 0;

      list.push(e);

    }

    list.sort((a, b) => b.dist - a.dist);

    ctx.globalCompositeOperation = 'lighter';

    for (const e of list) {

      const n = e.it;

      const r = (n.r / e.z) * FOCAL;

      if (r < 1) continue;

      // fully transparent from FIELD_NEB (5200u) out to the horizon, full by

      // a FIELD (2600u) in — smoothstep so the ramp itself has no kinks

      const t = Math.max(0, Math.min(1, (FIELD_NEB - e.dist) / (FIELD_NEB - FIELD)));

      const fade = t * t * (3 - 2 * t);

      const alpha = 0.5 * fade;

      ctx.save();

      ctx.globalAlpha = alpha;

      ctx.translate(e.x, e.y);

      ctx.rotate(n.rot);

      ctx.drawImage(nebulaTex[n.ci], -r, -r, r * 2, r * 2);

      ctx.restore();

    }

    ctx.globalCompositeOperation = 'source-over';

    ctx.globalAlpha = 1;

  }



  // Rotate a local point into world space, then translate & scale.

  // Yaw+pitch are one rotation matrix whose columns are the ship's right,

  // up and back axes in world space. The local nose (-Z) therefore maps to

  // exactly (sin h * cos p, sin p, -cos h * cos p) — the same direction

  // update() thrusts along — at every heading and pitch.

  function shipWorldPoint(v, out) {

    const s = SHIP_SCALE;

    const x = v[0] * s, y = v[1] * s, z = v[2] * s;

    // bank (visual roll) in the body frame about local forward (local Z)

    const cb = Math.cos(ship.bank), sb = Math.sin(ship.bank);

    const x1 = x * cb + y * sb;

    const y1 = -x * sb + y * cb;

    const z1 = z;

    const ch = Math.cos(ship.heading), sh = Math.sin(ship.heading);

    const cp = Math.cos(ship.pitch), sp2 = Math.sin(ship.pitch);

    out[0] = ship.pos[0] + ch * x1 - sh * sp2 * y1 - sh * cp * z1;

    out[1] = ship.pos[1] + cp * y1 - sp2 * z1;

    out[2] = ship.pos[2] + sh * x1 + ch * sp2 * y1 + ch * cp * z1;

    return out;

  }



  function worldShipPoint(v, cam, out) {

    const w = shipWorldPoint(v, SHIP_W);

    return project(w[0], w[1], w[2], cam, out);

  }



  function drawShip(cam, now) {

    // Precompute projected verts into the pool (19 verts, far under the pool size)

    for (let i = 0; i < shipVerts.length; i++) P_OK[i] = worldShipPoint(shipVerts[i], cam, P_VERTS[i]) ? 1 : 0;

    // Build face list with depth + normal (skip if any vert behind)

    faceList.length = 0;

    for (const f of shipFaces) {

      if (!P_OK[f[0]] || !P_OK[f[1]] || !P_OK[f[2]]) continue;

      const a = P_VERTS[f[0]], b = P_VERTS[f[1]], c = P_VERTS[f[2]];

      const rec = FACE_REC[faceList.length];

      rec.a = a; rec.b = b; rec.c = c;

      rec.z = (a.z + b.z + c.z) / 3;

      rec.k = f[3];

      faceList.push(rec);

    }

    faceList.sort((p, q) => q.z - p.z);



    for (const fc of faceList) {

      const key = fc.k;

      const base = shipColors[key];

      // face normal in camera-ish space via projected verts (approx)

      const bx = fc.b.x - fc.a.x, by = fc.b.y - fc.a.y;

      const fx = fc.c.x - fc.a.x, fy = fc.c.y - fc.a.y;

      const nx = bx * fy - fx * by;

      let shade = 0.55 + 0.45 * Math.abs(nx) / (Math.max(1, Math.sqrt(bx * bx + by * by)));

      shade = Math.min(1.2, shade);



      const col = key === 'g'

        ? base

        : [Math.min(255, base[0] * shade), Math.min(255, base[1] * shade), Math.min(255, base[2] * shade)];



      ctx.beginPath();

      ctx.moveTo(fc.a.x, fc.a.y);

      ctx.lineTo(fc.b.x, fc.b.y);

      ctx.lineTo(fc.c.x, fc.c.y);

      ctx.closePath();

      ctx.fillStyle = rgbStr(col[0] | 0, col[1] | 0, col[2] | 0);

      ctx.fill();

      if (key !== 'g') {

        ctx.strokeStyle = 'rgba(0,0,0,0.25)';

        ctx.lineWidth = 0.5;

        ctx.stroke();

      }

    }



    // Cockpit glow halo — baked once as a bitmap, so no gradient is built per frame

    const cp = worldShipPoint([0, 0.35, -0.4], cam, P_ONE);

    if (cp) {

      ctx.globalCompositeOperation = 'lighter';

      ctx.drawImage(cockpitGlow, cp.x - HALO_R / 2, cp.y - HALO_R / 2, HALO_R, HALO_R);

      ctx.globalCompositeOperation = 'source-over';

    }



    // Thruster flames at the REAR (two engines)

    drawThrusters(cam, now);

  }



  function drawThrusters(cam, now) {

    const thr = ship.throttle;

    if (thr < 0.04) return;

    const t = now * 0.02;

    const flick = 0.72 + 0.28 * Math.sin(t) + 0.14 * Math.sin(t * 2.7);

    const baseLen = (0.55 + 1.25 * thr) * flick;

    const glow = 0.25 + 0.75 * thr;



    ctx.globalCompositeOperation = 'lighter';

    for (const e of ENGINE_LOCAL) {

      const p0 = worldShipPoint(e, cam, P_ONE);

      if (!p0) continue;

      // flame extends further back (+Z local)

      const p1 = worldShipPoint([e[0], e[1], 1.32 + baseLen * 0.6], cam, P_TWO);

      const p2 = worldShipPoint([e[0], e[1], 1.32 + baseLen], cam, P_THREE);

      if (!p1 || !p2) continue;



      const grad = ctx.createLinearGradient(p0.x, p0.y, p2.x, p2.y);

      grad.addColorStop(0, 'rgba(180,235,255,' + alphaStr(0.9 * glow) + ')');

      grad.addColorStop(0.4, 'rgba(70,160,255,' + alphaStr(0.7 * glow) + ')');

      grad.addColorStop(1, 'rgba(40,90,255,0)');

      ctx.strokeStyle = grad;

      ctx.lineWidth = 5 * flick * (0.55 + 0.5 * thr);

      ctx.lineCap = 'round';

      ctx.beginPath();

      ctx.moveTo(p0.x, p0.y);

      ctx.quadraticCurveTo(p1.x, p1.y, p2.x, p2.y);

      ctx.stroke();



      // core glow

      ctx.fillStyle = 'rgba(200,240,255,' + alphaStr(0.5 * flick * glow) + ')';

      ctx.beginPath();

      ctx.arc(p0.x, p0.y, 3.2, 0, Math.PI * 2);

      ctx.fill();

    }

    ctx.globalCompositeOperation = 'source-over';

  }



  const AST_LIGHT = norm([0.42, 0.58, -0.7]); // fixed sun direction (world space)



  function drawAsteroids(cam) {

    const cp = cam.camPos;

    list.length = 0;

    for (const a of asteroids) {

      // infinite space: wrap around the ship

      if (a.x < ship.pos[0] - FIELD_AST) a.x += 2 * FIELD_AST; else if (a.x > ship.pos[0] + FIELD_AST) a.x -= 2 * FIELD_AST;

      if (a.y < ship.pos[1] - FIELD_AST) a.y += 2 * FIELD_AST; else if (a.y > ship.pos[1] + FIELD_AST) a.y -= 2 * FIELD_AST;

      if (a.z < ship.pos[2] - FIELD_AST) a.z += 2 * FIELD_AST; else if (a.z > ship.pos[2] + FIELD_AST) a.z -= 2 * FIELD_AST;

      const dx = a.x - cp[0], dy = a.y - cp[1], dz = a.z - cp[2];

      const dist = Math.sqrt(dx * dx + dy * dy + dz * dz);

      if (dist > FIELD_AST * Math.sqrt(3)) continue; // view distance, 3x the old 3640u

      // Pop-proof fade in (same idea as the nebulae, with a hard guard).

      // Two continuous factors, both pure functions of distance, so a wrap

      // (which can only land an asteroid >= ~7560u from the camera) always

      // lands it at EXACTLY 0 alpha. The runway is now ~5300u long (about

      // 40s of travel at max speed) and concave, so a rock is a faint speck

      // far away, becomes clear over many seconds, and eases up to solid:

      //   7000u -> ~8%   5500u -> ~46%   4500u -> ~70%   2800u -> ~98%

      //   guard  — hard zero within 300u of the far wrap edge (respawn zone)

      //   main   — smoothstep 7540u -> 2200u, gamma-lifted

      const guard = Math.max(0, Math.min(1, (7540 - dist) / 300));

      if (guard <= 0) continue; // guaranteed-invisible respawn zone

      const t = Math.max(0, Math.min(1, (7540 - dist) / 5340));

      const alpha = Math.pow(t * t * (3 - 2 * t), 0.7) * guard;

      if (alpha < 0.02) continue; // below this it's invisible anyway — skip work

      const p = project(a.x, a.y, a.z, cam, P_ONE);

      if (!p) continue;

      const e = ENTRY[list.length];

      e.it = a; e.x = p.x; e.y = p.y; e.z = p.z; e.dist = dist; e.fade = alpha;

      list.push(e);

    }

    list.sort((x, y) => y.dist - x.dist);



    for (const e of list) {

      if (e.z < 2) continue;

      ctx.globalAlpha = e.fade;

      const a = e.it;

      const s = a.scale;

      const c0 = Math.cos(a.rot[0]), s0 = Math.sin(a.rot[0]);

      const c1 = Math.cos(a.rot[1]), s1 = Math.sin(a.rot[1]);

      const c2 = Math.cos(a.rot[2]), s2 = Math.sin(a.rot[2]);

      // tumble matrix (same orientation as the original three-step rotation),

      // so a stored normal can be rotated with 9 multiplies instead of a cross

      // product plus a normalising sqrt per face.

      const m0 = c1 * c2, m1 = s0 * s1 * c2 - c0 * s2, m2 = c0 * s1 * c2 + s0 * s2;

      const m3 = c1 * s2, m4 = s0 * s1 * s2 + c0 * c2, m5 = c0 * s1 * s2 - s0 * c2;

      const m6 = -s1, m7 = s0 * c1, m8 = c0 * c1;



      for (let i = 0; i < a.verts.length; i++) {

        const v = a.verts[i];

        const x = v[0] * s, y = v[1] * s, z = v[2] * s;

        const lx = m0 * x + m1 * y + m2 * z;

        const ly = m3 * x + m4 * y + m5 * z;

        const lz = m6 * x + m7 * y + m8 * z;

        const o = i * 3;

        AST_LOCAL[o] = lx; AST_LOCAL[o + 1] = ly; AST_LOCAL[o + 2] = lz;

        P_OK[i] = project(a.x + lx, a.y + ly, a.z + lz, cam, P_VERTS[i]) ? 1 : 0;

      }



      faceList.length = 0;

      for (let fi = 0; fi < a.faces.length; fi++) {

        const f = a.faces[fi];

        if (!P_OK[f[0]] || !P_OK[f[1]] || !P_OK[f[2]]) continue;

        const A = P_VERTS[f[0]], B = P_VERTS[f[1]], C = P_VERTS[f[2]];

        const o0 = f[0] * 3, o1 = f[1] * 3, o2 = f[2] * 3;

        // stored unit normal, rotated by the tumble matrix

        const n = a.faceNormal[fi];

        const nx = m0 * n[0] + m1 * n[1] + m2 * n[2];

        const ny = m3 * n[0] + m4 * n[1] + m5 * n[2];

        const nz = m6 * n[0] + m7 * n[1] + m8 * n[2];

        // backface cull: normal must point toward the camera

        const fx = (AST_LOCAL[o0] + AST_LOCAL[o1] + AST_LOCAL[o2]) / 3;

        const fy = (AST_LOCAL[o0 + 1] + AST_LOCAL[o1 + 1] + AST_LOCAL[o2 + 1]) / 3;

        const fz = (AST_LOCAL[o0 + 2] + AST_LOCAL[o1 + 2] + AST_LOCAL[o2 + 2]) / 3;

        if (nx * (cp[0] - a.x - fx) + ny * (cp[1] - a.y - fy) + nz * (cp[2] - a.z - fz) <= 0) continue;

        // normal is already unit length, so the dot is cos(theta) directly

        const lit = LIT_LUT[Math.max(0, Math.min(255, ((nx * AST_LIGHT[0] + ny * AST_LIGHT[1] + nz * AST_LIGHT[2]) * 256) | 0))];

        const fc = a.faceCol[fi];

        const br = (a.shade / 100) * (0.28 + 0.95 * lit);

        const r = Math.min(255, fc[0] * br + 10);

        const g = Math.min(255, fc[1] * br + 10);

        const b = Math.min(255, fc[2] * br + 16);

        const rec = FACE_REC[faceList.length];

        rec.a = A; rec.b = B; rec.c = C;

        rec.z = (A.z + B.z + C.z) / 3;

        rec.col = rgbStr(r | 0, g | 0, b | 0);

        faceList.push(rec);

      }

      // A convex rock's backface-culled faces cannot overlap in projection, so

      // painter order is dead work here. Crater displacement breaks convexity

      // slightly: measured over random tumbles, 1.75% of drawn face area

      // overlaps and 0.9% would be painted in the wrong order (crater floor over

      // rim). Set PERF.sortAsteroids to true if you see that.

      if (PERF.sortAsteroids) faceList.sort((m, n) => n.z - m.z);

      for (const fc of faceList) {

        ctx.fillStyle = fc.col;

        ctx.beginPath();

        ctx.moveTo(fc.a.x, fc.a.y);

        ctx.lineTo(fc.b.x, fc.b.y);

        ctx.lineTo(fc.c.x, fc.c.y);

        ctx.closePath();

        ctx.fill();

      }

    }

    ctx.globalAlpha = 1;

  }



  const BAND_ALPHAS = [0.16, 0.3, 0.5];

  const BAND_COLORS = ['rgb(150,180,235)', 'rgb(235,225,215)', 'rgb(175,215,245)'];



  function drawSky(cam) {

    const cp = cam.camPos, xa = cam.xAxis, ya = cam.yAxis, za = cam.zAxis;

    ctx.globalCompositeOperation = 'lighter';

    // soft band glow with dust gaps

    for (const b of bandBlobs) {

      const cz = b.dir[0] * za[0] + b.dir[1] * za[1] + b.dir[2] * za[2];

      if (cz < 0.05) continue;

      const cx = b.dir[0] * xa[0] + b.dir[1] * xa[1] + b.dir[2] * xa[2];

      const cy = b.dir[0] * ya[0] + b.dir[1] * ya[1] + b.dir[2] * ya[2];

      const px = CX + (cx / cz) * FOCAL;

      const py = CY - (cy / cz) * FOCAL;

      // b.r is a world-space radius; the band lives on a unit-direction shell

      // of radius SKY_R, so convert it to an angular size first. Without the

      // /SKY_R these blobs are ~1.4M px wide and additive-blend the whole

      // screen to white.

      const r = Math.min(PERF.blobMaxR, (b.r / SKY_R / cz) * FOCAL);

      if (r < 3 || px < -r || px > W + r || py < -r || py > H + r) continue;

      ctx.globalAlpha = b.a * Math.min(1, cz * 1.5);

      ctx.drawImage(b.tex, px - r, py - r, r * 2, r * 2);

    }

    ctx.globalAlpha = 1;

    // faint deep-field dusting hugging the band

    const paths = [new Path2D(), new Path2D(), new Path2D(), new Path2D(), new Path2D(),

                   new Path2D(), new Path2D(), new Path2D(), new Path2D()];

    for (const st of bandStars) {

      const cz = st.dir[0] * za[0] + st.dir[1] * za[1] + st.dir[2] * za[2];

      if (cz <= 0.05) continue;

      const cx = st.dir[0] * xa[0] + st.dir[1] * xa[1] + st.dir[2] * xa[2];

      const cy = st.dir[0] * ya[0] + st.dir[1] * ya[1] + st.dir[2] * ya[2];

      const px = CX + (cx / cz) * FOCAL;

      if (px < -2 || px > W + 2) continue;

      const py = CY - (cy / cz) * FOCAL;

      if (py < -2 || py > H + 2) continue;

      paths[st.c * 3 + st.b].rect(px, py, st.s, st.s);

    }

    for (let i = 0; i < 9; i++) {

      ctx.globalAlpha = BAND_ALPHAS[i % 3];

      ctx.fillStyle = BAND_COLORS[(i / 3) | 0];

      ctx.fill(paths[i]);

    }

    ctx.globalAlpha = 1;

    ctx.globalCompositeOperation = 'source-over';

  }



  function drawFilaments(cam) {

    const cp = cam.camPos, xa = cam.xAxis, ya = cam.yAxis, za = cam.zAxis;

    ctx.globalCompositeOperation = 'lighter';

    const cluster = new Path2D();



    for (const f of filaments) {

      // wrap the whole strand around the ship (node data stays untouched)

      const c0 = f.nodes[0];

      for (let i = 0; i < 3; i++) {

        const p = c0[i] + f.off[i];

        if (p < ship.pos[i] - FIELD_FIL) f.off[i] += 2 * FIELD_FIL;

        else if (p > ship.pos[i] + FIELD_FIL) f.off[i] -= 2 * FIELD_FIL;

      }



      // Bounding-sphere cull. filFade is exactly zero past FIELD_FIL, so if the

      // nearest point of the strand is beyond that the whole strand is invisible

      // for sure — one distance test instead of projecting 35 points. The screen

      // test uses the same padding as before, so it can never reject a strand

      // that had something to draw.

      const gx = f.center[0] + f.off[0], gy = f.center[1] + f.off[1], gz = f.center[2] + f.off[2];

      let dx = gx - cp[0], dy = gy - cp[1], dz = gz - cp[2];

      const gd = Math.sqrt(dx * dx + dy * dy + dz * dz);

      if (gd - f.radius > FIELD_FIL) continue;

      const gcz = dx * za[0] + dy * za[1] + dz * za[2];

      // Only reject if no point of the sphere could pass the per-point depth

      // test (cz >= 40). A strand whose centre is close to the camera can still

      // have a visible far end.

      if (gcz + f.radius < 40) continue;

      const gpx = CX + ((dx * xa[0] + dy * xa[1] + dz * xa[2]) / gcz) * FOCAL;

      const gpy = CY - ((dx * ya[0] + dy * ya[1] + dz * ya[2]) / gcz) * FOCAL;

      // Conservative projected radius: a point at the front of the sphere

      // projects further off-centre than one at the centre, so bound it with the

      // nearest possible depth. This can only reject strands that had nothing to

      // draw, never part of one.

      const near = gcz - f.radius;

      if (near > 0) {

        const sr = f.radius * FOCAL / near;

        if (gpx < -300 - sr || gpx > W + 300 + sr || gpy < -300 - sr || gpy > H + 300 + sr) continue;

      }



      const n = f.pts.length;

      for (let i = 0; i < n; i++) P_OK[i] = 0;



      // project the smoothed polyline once

      for (let i = 0; i < n; i++) {

        const nd = f.pts[i];

        const x = nd[0] + f.off[0], y = nd[1] + f.off[1], z = nd[2] + f.off[2];

        const px2 = x - cp[0], py2 = y - cp[1], pz2 = z - cp[2];

        const cz = px2 * za[0] + py2 * za[1] + pz2 * za[2];

        const fade = filFade(Math.sqrt(px2 * px2 + py2 * py2 + pz2 * pz2));

        if (cz < 40 || fade <= 0.01) continue;

        const sx = CX + ((px2 * xa[0] + py2 * xa[1] + pz2 * xa[2]) / cz) * FOCAL;

        const sy = CY - ((px2 * ya[0] + py2 * ya[1] + pz2 * ya[2]) / cz) * FOCAL;

        if (sx < -300 || sx > W + 300 || sy < -300 || sy > H + 300) continue;

        const p = P_FIL[i];

        p.x = sx; p.y = sy; p.z = cz; p.fade = fade;

        P_OK[i] = 1;

      }



      // One stroke per run of segments sharing a quantised alpha, instead of one

      // stroke per segment. Measured over random views: ~300 strokes/frame

      // become ~39. A gap in the polyline ends the run and starts a new path.

      for (let pass = 0; pass < 2; pass++) {

        const mult = pass === 0 ? 0.1 : 0.3;

        const minW = pass === 0 ? 1.5 : 0.6;

        const maxW = pass === 0 ? 14 : 6;

        const scale = pass === 0 ? 2.2 : 0.45;

        let bucket = -1, cnt = 0, wsum = 0;

        for (let i = 0; i + 1 < n; i++) {

          if (!P_OK[i] || !P_OK[i + 1]) { flushRun(f.colorStr, bucket, cnt, wsum); cnt = 0; wsum = 0; bucket = -1; continue; }

          const A = P_FIL[i], B = P_FIL[i + 1];

          const a = (A.fade + B.fade) * 0.5 * f.glow * mult;

          const wpx = f.w * FOCAL / ((A.z + B.z) * 0.5);

          const w = Math.min(maxW, Math.max(minW, wpx * scale));

          const b = Math.min(63, (a * 63) | 0);

          if (b !== bucket) {

            flushRun(f.colorStr, bucket, cnt, wsum);

            bucket = b; cnt = 0; wsum = 0;

            ctx.beginPath();

          }

          ctx.moveTo(A.x, A.y);

          ctx.lineTo(B.x, B.y);

          cnt++; wsum += w;

        }

        flushRun(f.colorStr, bucket, cnt, wsum);

      }



      // galaxy clusters gathered at the knots

      for (let i = 0; i < f.nodes.length; i++) {

        const nd = f.nodes[i];

        const x = nd[0] + f.off[0], y = nd[1] + f.off[1], z = nd[2] + f.off[2];

        const dxk = x - cp[0], dyk = y - cp[1], dzk = z - cp[2];

        const cz = dxk * za[0] + dyk * za[1] + dzk * za[2];

        const fade = filFade(Math.sqrt(dxk * dxk + dyk * dyk + dzk * dzk));

        if (cz < 40 || fade <= 0.05) continue;

        const px = CX + ((dxk * xa[0] + dyk * xa[1] + dzk * xa[2]) / cz) * FOCAL;

        const py = CY - ((dxk * ya[0] + dyk * ya[1] + dzk * ya[2]) / cz) * FOCAL;

        if (px < -80 || px > W + 80 || py < -80 || py > H + 80) continue;

        const hs = Math.min(120, 120 * FOCAL / cz);

        ctx.globalAlpha = fade * 0.3 * f.glow;

        ctx.drawImage(softCool, px - hs / 2, py - hs / 2, hs, hs);

        ctx.globalAlpha = 1;

        const knots = f.knots[i];

        for (let k = 0; k < knots.length; k++) {

          const kx = x + knots[k][0] - cp[0], ky = y + knots[k][1] - cp[1], kz = z + knots[k][2] - cp[2];

          const kcz = kx * za[0] + ky * za[1] + kz * za[2];

          if (kcz < 40) continue;

          const qx = CX + ((kx * xa[0] + ky * xa[1] + kz * xa[2]) / kcz) * FOCAL;

          const qy = CY - ((kx * ya[0] + ky * ya[1] + kz * ya[2]) / kcz) * FOCAL;

          if (qx < -2 || qx > W + 2 || qy < -2 || qy > H + 2) continue;

          cluster.rect(qx, qy, 1, 1);

        }

      }

    }

    ctx.globalAlpha = 0.45;

    ctx.fillStyle = 'rgb(215,230,255)';

    ctx.fill(cluster);

    ctx.globalAlpha = 1;

    ctx.globalCompositeOperation = 'source-over';

  }



  function drawGalaxies(cam) {

    const G_MAX = FIELD_GAL * Math.sqrt(3);

    list.length = 0;

    for (const g of galaxies) {

      if (g.x < ship.pos[0] - FIELD_GAL) g.x += 2 * FIELD_GAL;

      else if (g.x > ship.pos[0] + FIELD_GAL) g.x -= 2 * FIELD_GAL;

      if (g.y < ship.pos[1] - FIELD_GAL) g.y += 2 * FIELD_GAL;

      else if (g.y > ship.pos[1] + FIELD_GAL) g.y -= 2 * FIELD_GAL;

      if (g.z < ship.pos[2] - FIELD_GAL) g.z += 2 * FIELD_GAL;

      else if (g.z > ship.pos[2] + FIELD_GAL) g.z -= 2 * FIELD_GAL;

      const dx = g.x - cam.camPos[0], dy = g.y - cam.camPos[1], dz = g.z - cam.camPos[2];

      const dist = Math.sqrt(dx * dx + dy * dy + dz * dz);

      if (dist > G_MAX) continue;

      const t = Math.max(0, Math.min(1, (FIELD_GAL - dist) / (FIELD_GAL - FIELD)));

      const fade = smoothstep(t);

      if (fade < 0.01) continue;

      const p = project(g.x, g.y, g.z, cam, P_ONE);

      if (!p) continue;

      const e = ENTRY[list.length];

      e.it = g; e.x = p.x; e.y = p.y; e.z = p.z; e.dist = dist; e.fade = fade;

      list.push(e);

    }

    list.sort((a, b) => b.dist - a.dist);

    ctx.globalCompositeOperation = 'lighter';

    for (const e of list) {

      const g = e.it;

      const r = (g.r / e.z) * FOCAL;

      if (r < 1.5) continue;

      ctx.save();

      ctx.globalAlpha = 0.62 * e.fade;

      ctx.translate(e.x, e.y);

      ctx.rotate(g.rot);

      ctx.scale(1, g.squash);

      ctx.drawImage(galaxyTex[g.ci], -r, -r, r * 2, r * 2);

      ctx.restore();

    }

    ctx.globalAlpha = 1;

    ctx.globalCompositeOperation = 'source-over';

  }



  function drawPlanets(cam) {

    const P_MAX = FIELD_PLANET * Math.sqrt(3);

    list.length = 0;

    for (const pl of planets) {

      for (let i = 0; i < 3; i++) {

        if (pl.x < ship.pos[0] - FIELD_PLANET) pl.x += 2 * FIELD_PLANET;

        else if (pl.x > ship.pos[0] + FIELD_PLANET) pl.x -= 2 * FIELD_PLANET;

        if (pl.y < ship.pos[1] - FIELD_PLANET) pl.y += 2 * FIELD_PLANET;

        else if (pl.y > ship.pos[1] + FIELD_PLANET) pl.y -= 2 * FIELD_PLANET;

        if (pl.z < ship.pos[2] - FIELD_PLANET) pl.z += 2 * FIELD_PLANET;

        else if (pl.z > ship.pos[2] + FIELD_PLANET) pl.z -= 2 * FIELD_PLANET;

      }

      const dx = pl.x - cam.camPos[0], dy = pl.y - cam.camPos[1], dz = pl.z - cam.camPos[2];

      const dist = Math.sqrt(dx * dx + dy * dy + dz * dz);

      if (dist > P_MAX) continue;

      const t = Math.max(0, Math.min(1, (FIELD_PLANET - dist) / (FIELD_PLANET - FIELD)));

      const fade = smoothstep(t);

      if (fade < 0.01) continue;

      const p = project(pl.x, pl.y, pl.z, cam, P_ONE);

      if (!p) continue;

      const r = (pl.r / p.z) * FOCAL;

      if (r < 1.5) continue;

      const e = ENTRY[list.length];

      e.it = pl; e.x = p.x; e.y = p.y; e.z = p.z; e.r = r; e.dist = dist; e.fade = fade;

      e.dx = dx; e.dy = dy; e.dz = dz;

      list.push(e);

    }

    list.sort((a, b) => b.dist - a.dist);



    // Sun direction in camera space: once per frame, not once per planet.

    const lx = SUN_DIR[0] * cam.xAxis[0] + SUN_DIR[1] * cam.xAxis[1] + SUN_DIR[2] * cam.xAxis[2];

    const ly = SUN_DIR[0] * cam.yAxis[0] + SUN_DIR[1] * cam.yAxis[1] + SUN_DIR[2] * cam.yAxis[2];



    for (const e of list) {

      const pl = e.it, px = e.x, py = e.y, r = e.r, fade = e.fade;

      const dl = Math.sqrt(e.dx * e.dx + e.dy * e.dy + e.dz * e.dz) || 1;

      const f = (SUN_DIR[0] * e.dx + SUN_DIR[1] * e.dy + SUN_DIR[2] * e.dz) / dl; // +1 = night side to us

      const phase = (1 - f) * 0.5; // 1 = full, 0 = new

      let ux = lx, uy = -ly;

      const ul = Math.sqrt(ux * ux + uy * uy);

      if (ul < 1e-4) { ux = 1; uy = 0; } else { ux /= ul; uy /= ul; }



      const ringN = pl.ring ? ringProjection(pl, cam) : 0;

      if (ringN) strokeRing(pl, ringN, 1, fade);



      // surface

      ctx.save();

      ctx.beginPath();

      ctx.arc(px, py, r, 0, TAU);

      ctx.clip();

      ctx.globalAlpha = fade;

      ctx.save();

      ctx.translate(px, py);

      ctx.rotate(pl.spin);

      ctx.drawImage(planetTex[pl.tex], -r, -r, r * 2, r * 2);

      ctx.restore();

      // day/night terminator multiplied over the surface only

      const soft = 0.24;

      const grad = ctx.createLinearGradient(px - ux * r, py - uy * r, px + ux * r, py + uy * r);

      const dark = 'rgb(11,13,22)', light = 'rgb(255,255,255)';

      grad.addColorStop(0, dark);

      grad.addColorStop(Math.min(1, phase), dark);

      grad.addColorStop(Math.max(0, Math.min(1, phase + soft)), light);

      grad.addColorStop(1, light);

      ctx.globalCompositeOperation = 'multiply';

      ctx.fillStyle = grad;

      ctx.beginPath();

      ctx.arc(px, py, r, 0, TAU);

      ctx.fill();

      ctx.restore();



      // atmosphere rim

      const ac = pl.atmoStr;

      ctx.globalCompositeOperation = 'lighter';

      const ag = ctx.createRadialGradient(px, py, r * 0.82, px, py, r * 1.3);

      ag.addColorStop(0, 'rgba(' + ac + ',0)');

      ag.addColorStop(0.45, 'rgba(' + ac + ',' + alphaStr(0.2 * fade) + ')');

      ag.addColorStop(1, 'rgba(' + ac + ',0)');

      ctx.fillStyle = ag;

      ctx.beginPath();

      ctx.arc(px, py, r * 1.3, 0, TAU);

      ctx.fill();

      ctx.globalCompositeOperation = 'source-over';



      if (ringN) strokeRing(pl, ringN, 2, fade);

    }

    ctx.globalAlpha = 1;

  }



  // Ring points are classified by depth against the planet centre, so the

  // far half is drawn behind the body and the near half over it. Points go

  // into the P_RING pool and the front/behind flags into RING_FRONT; the

  // function returns the count (0 = nothing to draw).

  function ringProjection(pl, cam) {

    const centre = project(pl.x, pl.y, pl.z, cam, P_CENTER);

    if (!centre) return 0;

    const N = 56;

    for (let i = 0; i <= N; i++) {

      const a = i / N * TAU;

      const ca = Math.cos(a), sa = Math.sin(a);

      const R = pl.r * pl.ringR;

      const q = project(pl.x + (pl.ringA[0] * ca + pl.ringB[0] * sa) * R,

                        pl.y + (pl.ringA[1] * ca + pl.ringB[1] * sa) * R,

                        pl.z + (pl.ringA[2] * ca + pl.ringB[2] * sa) * R, cam, P_RING[i]);

      RING_FRONT[i] = q ? (q.z < centre.z ? 2 : 1) : 0;

    }

    return N + 1;

  }



  function strokeRing(pl, n, front, fade) {

    ctx.lineCap = 'round';

    const style = 'rgba(' + pl.atmoStr + ',' + alphaStr(0.26 * fade) + ')'; // built once, not per segment

    for (let i = 0; i + 1 < n; i++) {

      if (RING_FRONT[i] !== front || RING_FRONT[i + 1] !== front) continue;

      const A = P_RING[i], B = P_RING[i + 1];

      const z = (A.z + B.z) * 0.5;

      ctx.strokeStyle = style;

      ctx.lineWidth = Math.max(0.7, pl.ringW * FOCAL / z); // width still varies with depth

      ctx.beginPath();

      ctx.moveTo(A.x, A.y);

      ctx.lineTo(B.x, B.y);

      ctx.stroke();

    }

  }



  function drawMeteors(cam) {

    if (!meteors.length) return;

    ctx.globalCompositeOperation = 'lighter';

    ctx.lineCap = 'round';

    for (const m of meteors) {

      const head = project(m.x, m.y, m.z, cam, P_ONE);

      if (!head) continue;

      const sp = Math.sqrt(m.vx * m.vx + m.vy * m.vy + m.vz * m.vz) || 1;

      const tl = sp * m.trail;

      const tail = project(m.x - m.vx / sp * tl, m.y - m.vy / sp * tl, m.z - m.vz / sp * tl, cam, P_TWO);

      if (!tail) continue;

      const t = m.life / m.max;

      let env = 1;

      if (t < 0.18) env = t / 0.18;

      else if (t > 0.6) env = Math.max(0, (1 - t) / 0.4);

      if (env <= 0.02 || !tail) continue;

      const cs = m.warm ? '255,226,190' : '205,235,255';

      const g = ctx.createLinearGradient(head.x, head.y, tail.x, tail.y);

      g.addColorStop(0, 'rgba(' + cs + ',' + alphaStr(0.95 * env) + ')');

      g.addColorStop(0.35, 'rgba(' + cs + ',' + alphaStr(0.4 * env) + ')');

      g.addColorStop(1, 'rgba(' + cs + ',0)');

      ctx.strokeStyle = g;

      ctx.lineWidth = m.w;

      ctx.beginPath();

      ctx.moveTo(head.x, head.y);

      ctx.lineTo(tail.x, tail.y);

      ctx.stroke();

      const hs = (m.fireball ? 52 : 24) * env;

      ctx.globalAlpha = 0.8 * env;

      ctx.drawImage(m.warm ? softWarm : softCool, head.x - hs / 2, head.y - hs / 2, hs, hs);

      ctx.globalAlpha = 1;

    }

    ctx.globalCompositeOperation = 'source-over';

  }



  function drawExhaust(cam) {

    if (!exhaust.length) return;

    ctx.globalCompositeOperation = 'lighter';

    for (const p of exhaust) {

      const q = project(p.x, p.y, p.z, cam, P_ONE);

      if (!q) continue;

      const t = p.life / p.max;

      const a = (1 - t) * (1 - t) * 0.55;

      let hs = p.r * (1 + t * 2.4) * 2 * FOCAL / q.z;

      if (hs < 1) continue;

      if (hs > 34) hs = 34;

      ctx.globalAlpha = a;

      ctx.drawImage(softCool, q.x - hs / 2, q.y - hs / 2, hs, hs);

    }

    ctx.globalAlpha = 1;

    ctx.globalCompositeOperation = 'source-over';

  }



  const DUST_ALPHAS = [0.1, 0.22, 0.36];

  function drawDust(cam) {

    const cp = cam.camPos;

    const paths = [new Path2D(), new Path2D(), new Path2D()];

    const TRAIL = 0.05; // motion-blur trail time — the speed cue

    const vx = ship.vel[0] * TRAIL, vy = ship.vel[1] * TRAIL, vz = ship.vel[2] * TRAIL;

    for (const d of dust) {

      if (d.x < cp[0] - DUST_R) d.x += 2 * DUST_R;

      else if (d.x > cp[0] + DUST_R) d.x -= 2 * DUST_R;

      if (d.y < cp[1] - DUST_R) d.y += 2 * DUST_R;

      else if (d.y > cp[1] + DUST_R) d.y -= 2 * DUST_R;

      if (d.z < cp[2] - DUST_R) d.z += 2 * DUST_R;

      else if (d.z > cp[2] + DUST_R) d.z -= 2 * DUST_R;

      const dx = d.x - cp[0], dy = d.y - cp[1], dz = d.z - cp[2];

      const dist = Math.sqrt(dx * dx + dy * dy + dz * dz);

      if (dist > DUST_R || dist < 12) continue;

      const cz = dx * cam.zAxis[0] + dy * cam.zAxis[1] + dz * cam.zAxis[2];

      if (cz < 20) continue;

      const cx = dx * cam.xAxis[0] + dy * cam.xAxis[1] + dz * cam.xAxis[2];

      const cy = dx * cam.yAxis[0] + dy * cam.yAxis[1] + dz * cam.yAxis[2];

      const px = CX + (cx / cz) * FOCAL;

      if (px < -20 || px > W + 20) continue;

      const py = CY - (cy / cz) * FOCAL;

      if (py < -20 || py > H + 20) continue;

      // the mote appeared at here a moment ago: that's the streak

      const cz2 = cz + (vx * cam.zAxis[0] + vy * cam.zAxis[1] + vz * cam.zAxis[2]);

      if (cz2 < 20) continue;

      const cx2 = cx + vx * cam.xAxis[0] + vy * cam.xAxis[1] + vz * cam.xAxis[2];

      const cy2 = cy + vx * cam.yAxis[0] + vy * cam.yAxis[1] + vz * cam.yAxis[2];

      const qx = CX + (cx2 / cz2) * FOCAL;

      const qy = CY - (cy2 / cz2) * FOCAL;

      const bucket = Math.min(2, ((1 - dist / DUST_R) * 3) | 0);

      const path = paths[bucket];

      path.moveTo(px, py);

      path.lineTo(qx, qy);

    }

    ctx.globalCompositeOperation = 'lighter';

    ctx.strokeStyle = 'rgb(200,225,255)';

    ctx.lineWidth = 1;

    for (let i = 0; i < 3; i++) {

      ctx.globalAlpha = DUST_ALPHAS[i];

      ctx.stroke(paths[i]);

    }

    ctx.globalAlpha = 1;

    ctx.globalCompositeOperation = 'source-over';

  }



  function drawCursor() {

    if (cursorAlpha <= 0.01) return;

    ctx.save();

    ctx.globalAlpha = cursorAlpha;

    ctx.strokeStyle = '#cfeaff';

    ctx.fillStyle = '#cfeaff';

    ctx.lineWidth = 1.5;

    ctx.lineCap = 'round';

    ctx.beginPath();

    ctx.moveTo(mouseX - 13, mouseY); ctx.lineTo(mouseX - 5, mouseY);

    ctx.moveTo(mouseX + 5, mouseY);  ctx.lineTo(mouseX + 13, mouseY);

    ctx.moveTo(mouseX, mouseY - 13); ctx.lineTo(mouseX, mouseY - 5);

    ctx.moveTo(mouseX, mouseY + 5);  ctx.lineTo(mouseX, mouseY + 13);

    ctx.stroke();

    ctx.beginPath();

    ctx.arc(mouseX, mouseY, 1.6, 0, Math.PI * 2);

    ctx.fill();

    ctx.restore();

  }



  // ------------------------------------------------------------------

  // Main loop

  // ------------------------------------------------------------------

  function frame(now) {

    let dt = (now - last) / 1000;

    last = now;



    // Fixed: guard against zero or negative dt to avoid NaN in yawRate.

    if (dt <= 0) {

      requestAnimationFrame(frame);

      return;

    }



    if (dt > 0.05) dt = 0.05; // clamp big gaps



    update(dt);



    const cam = cameraBasis(dt);

    spawnMeteors(cam, now);



    drawBackground();

    drawSky(cam);

    drawNebulae(cam);

    drawGalaxies(cam);

    drawFilaments(cam);

    drawStars(cam);

    drawPlanets(cam);

    drawAsteroids(cam);

    drawExhaust(cam);

    drawMeteors(cam);

    drawDust(cam);

    drawShip(cam, now);



    if (vignetteLayer) {

      ctx.drawImage(vignetteLayer, 0, 0, W, H);

    }



    // Cursor fade: visible while the mouse moved within the last second,

    // eases out after that, eases back in on movement.

    {

      const idle = now - lastMove;

      const target = idle < 1000 ? 1 : 0;

      const speed = target === 1 ? 12 : 4;

      cursorAlpha += (target - cursorAlpha) * Math.min(1, speed * dt);

      if (target === 0 && cursorAlpha < 0.01) cursorAlpha = 0;

      else if (target === 1 && cursorAlpha > 0.99) cursorAlpha = 1;

    }

    drawCursor();



    requestAnimationFrame(frame);

  }



  // Fixed: ensure a valid camera basis exists before the first click.

  cameraBasis(0.016);

  requestAnimationFrame(frame);

})();

</script>
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</html>