/* CSS Reset and Base Styles */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  /* Light theme: Crisp, minimal, highly professional */
  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc; /* subtle off-white for contrast zones */
  --text-primary: #0f172a; /* deep slate */
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --accent-primary: #2563eb; /* sleek royal blue */
  --accent-secondary: #1d4ed8;
  --border-color: #e2e8f0;
  
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.05), 0 2px 4px -2px rgb(0 0 0 / 0.05);
  --shadow-lg: 0 10px 25px -3px rgb(0 0 0 / 0.05), 0 4px 6px -4px rgb(0 0 0 / 0.05);
  --radius-md: 12px;
  --radius-button: 6px;
}

[data-theme="dark"] {
  /* Dark theme: Deep midnight, soft contrast */
  --bg-primary: #020617;
  --bg-secondary: #0f172a;
  --text-primary: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-muted: #64748b;
  --accent-primary: #3b82f6;
  --accent-secondary: #60a5fa;
  --border-color: #1e293b;
  
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.5);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.3), 0 2px 4px -2px rgb(0 0 0 / 0.3);
  --shadow-lg: 0 10px 25px -3px rgb(0 0 0 / 0.3), 0 4px 6px -4px rgb(0 0 0 / 0.3);
}

body {
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  line-height: 1.7;
  color: var(--text-primary);
  background-color: var(--bg-primary);
  transition: background-color 0.3s ease, color 0.3s ease;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.2;
  margin-bottom: 0.75rem;
  letter-spacing: -0.02em;
}

h1 {
  font-size: 3.5rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: 1.25rem;
  color: var(--text-primary);
}

h2 {
  font-size: 2rem;
  margin-bottom: 2.5rem;
  text-align: center;
  position: relative;
  padding-bottom: 1rem;
}

h2::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 40px;
  height: 2px;
  background-color: var(--accent-primary);
  border-radius: 2px;
}

h3 {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--text-primary);
}

p {
  margin-bottom: 1.25rem;
  color: var(--text-secondary);
  font-weight: 400;
}

a {
  color: var(--accent-primary);
  text-decoration: none;
  transition: color 0.2s ease;
}

a:hover {
  text-decoration: underline;
  text-underline-offset: 4px;
}

ul {
  padding-left: 1.2rem;
  margin-bottom: 1.25rem;
  color: var(--text-secondary);
}

li {
  margin-bottom: 0.5rem;
}

/* Layout */
.container {
  max-width: 900px; /* narrowed for better reading length */
  margin: 0 auto;
  padding: 0 1.5rem;
}

.section {
  padding: 6rem 0;
  border-bottom: 1px solid var(--border-color);
}
.section:last-child {
  border-bottom: none;
}

/* Header */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  background: var(--bg-primary);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border-color);
  z-index: 1000;
  background-color: color-mix(in srgb, var(--bg-primary) 85%, transparent);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 1.5rem;
  max-width: 1200px;
  margin: 0 auto;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-weight: 600;
  font-size: 1.1rem;
  color: var(--text-primary);
}

.brand:hover {
  text-decoration: none;
}

.logo {
  width: 32px;
  height: 32px;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 2rem;
  list-style: none;
  margin-bottom: 0;
}

.nav-links a {
  font-weight: 500;
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.nav-links a:hover {
  color: var(--text-primary);
  text-decoration: none;
}

.nav-toggle {
  display: none;
  background: none;
  border: none;
  font-size: 1.5rem;
  color: var(--text-primary);
  cursor: pointer;
}

/* Hero Section */
.hero {
  padding: 10rem 0 6rem;
  text-align: center;
}

.profile-container {
  margin-bottom: 2.5rem;
}

.profile-avatar {
  width: 140px;
  height: 140px;
  margin: 0 auto;
  display: block;
  border-radius: 50%;
  object-fit: cover;
  border: 1px solid var(--border-color);
  box-shadow: var(--shadow-md);
}

.hero-subtitle {
  font-size: 1.25rem;
  max-width: 650px;
  margin: 0 auto 2.5rem;
  color: var(--text-secondary);
  line-height: 1.8;
}

.cta {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 3rem;
}

.quick-facts {
  display: flex;
  gap: 2rem;
  justify-content: center;
  flex-wrap: wrap;
  list-style: none;
  font-size: 0.9rem;
  color: var(--text-secondary);
  padding: 0;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.75rem 1.5rem;
  border-radius: var(--radius-button);
  font-weight: 500;
  text-decoration: none;
  cursor: pointer;
  transition: all 0.2s ease;
  font-size: 0.95rem;
  border: 1px solid transparent;
}

.btn:hover {
  text-decoration: none;
}

.btn.primary {
  background-color: var(--text-primary);
  color: var(--bg-primary);
}

.btn.primary:hover {
  background-color: var(--text-secondary);
}

.btn:not(.primary):not(.ghost) {
  background: transparent;
  color: var(--text-primary);
  border-color: var(--border-color);
}

.btn:not(.primary):not(.ghost):hover {
  background: var(--bg-secondary);
  border-color: var(--text-muted);
}

.btn.ghost {
  background: transparent;
  color: var(--text-secondary);
}

.btn.ghost:hover {
  background: var(--bg-secondary);
  color: var(--text-primary);
}

/* Cards / Grid Layouts */
.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
}

.card {
  background: transparent;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 2rem;
  transition: transform 0.4s cubic-bezier(0.16, 1, 0.3, 1), box-shadow 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--text-muted);
}

.card.kpi {
  text-align: center;
  padding: 2rem 1.5rem;
}

.card.kpi h3 {
  font-size: 2.25rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 0.5rem;
}

.card.kpi p {
  font-size: 0.9rem;
  margin-bottom: 0;
}

.card.project h3 {
  margin-bottom: 1rem;
}

/* Timeline / Experience */
.timeline {
  list-style: none;
  position: relative;
  padding-left: 0;
  margin-left: 1rem;
  border-left: 1px solid var(--border-color);
}

.timeline > li {
  position: relative;
  margin-bottom: 3rem;
  padding-left: 2.5rem;
}

.timeline > li::before {
  content: '';
  position: absolute;
  left: -5px;
  top: 6px;
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background: var(--text-muted);
}

.time {
  font-size: 0.85rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  margin-bottom: 0.5rem;
  display: block;
}

.content {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.5rem 2rem;
  margin-top: 0.5rem;
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.content:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.content h3 {
  font-size: 1.15rem;
  margin-bottom: 1rem;
}

.content ul {
  padding-left: 1.2rem;
}

/* Case Studies */
.cases {
  display: grid;
  gap: 1rem;
}

.case {
  background: transparent;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  overflow: hidden;
  transition: border-color 0.2s ease;
}

.case[open] {
  border-color: var(--text-muted);
}

.case summary {
  padding: 1.5rem;
  cursor: pointer;
  list-style: none;
  display: flex;
  flex-direction: column;
}

.case summary::-webkit-details-marker {
  display: none;
}

.case summary h3 {
  margin-bottom: 0.5rem;
}

.case summary .tags {
  margin-top: 0.5rem;
}

.case-details {
  padding: 0 1.5rem 1.5rem;
}

.case-details h4 {
  font-size: 1rem;
  color: var(--text-primary);
  margin: 1.5rem 0 0.5rem;
  font-weight: 600;
}

/* Tags and Chips (Minimalist) */
.tags {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  padding: 0;
}

.tags span {
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border-color);
  padding: 0.2rem 0.6rem;
  border-radius: 4px;
  font-size: 0.75rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.02em;
}

.chips {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  list-style: none;
  margin-bottom: 2rem;
  padding: 0;
}

.chips li {
  background: transparent;
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  padding: 0.4rem 1rem;
  border-radius: 4px;
  font-size: 0.85rem;
  font-weight: 500;
}

.sub {
  font-size: 1.1rem;
  margin: 2.5rem 0 1rem;
  color: var(--text-primary);
  font-weight: 600;
}

.edu {
  list-style: none;
  margin-bottom: 2rem;
  padding: 0;
}

.edu li {
  margin-bottom: 0.5rem;
  color: var(--text-secondary);
}

/* Contact */
.contact {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
  margin-top: 2rem;
}

/* Footer */
.site-footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: 3rem 0;
  text-align: center;
}

.site-footer small {
  color: var(--text-muted);
}

/* Theme Toggle */
#themeToggle {
  background: none;
  border: none;
  font-size: 1.2rem;
  cursor: pointer;
  padding: 0.5rem;
  border-radius: 50%;
  color: var(--text-secondary);
  transition: color 0.2s ease, background-color 0.2s ease;
  display: flex;
  align-items: center;
  justify-content: center;
}

#themeToggle:hover {
  background: var(--bg-secondary);
  color: var(--text-primary);
}

/* Responsive */
@media (max-width: 768px) {
  .nav-toggle {
    display: block;
  }

  .nav-links {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: var(--bg-primary);
    border-top: 1px solid var(--border-color);
    flex-direction: column;
    padding: 1rem;
    gap: 1rem;
    transform: translateY(-10px);
    opacity: 0;
    visibility: hidden;
    transition: all 0.2s ease;
    box-shadow: var(--shadow-sm);
  }

  .nav-links.active {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }

  h1 {
    font-size: 2.5rem;
  }

  /* Narrower container for mobile */
  .hero {
    padding: 7rem 0 4rem;
  }
}

/* Animation */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(15px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.card, .timeline li, .case {
  animation: fadeInUp 0.7s cubic-bezier(0.16, 1, 0.3, 1) both;
}

/* Staggered animation */
.card:nth-child(2) { animation-delay: 0.1s; }
.card:nth-child(3) { animation-delay: 0.2s; }
.card:nth-child(4) { animation-delay: 0.3s; }
.card:nth-child(5) { animation-delay: 0.4s; }
.card:nth-child(6) { animation-delay: 0.5s; }
.card:nth-child(7) { animation-delay: 0.6s; }
.card:nth-child(8) { animation-delay: 0.7s; }

html {
  scroll-behavior: smooth;
}