/* ===== RESET & BASE ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg: #080b14;
  --bg2: #0d1120;
  --surface: rgba(255,255,255,0.04);
  --surface2: rgba(255,255,255,0.07);
  --border: rgba(255,255,255,0.08);
  --text: #e2e8f0;
  --text2: #94a3b8;
  --text3: #475569;
  --mono: 'JetBrains Mono', monospace;
  --sans: 'Inter', sans-serif;
}

html { scroll-behavior: smooth; }

body {
  font-family: var(--sans);
  background: var(--bg);
  color: var(--text);
  overflow-x: hidden;
  line-height: 1.6;
}

/* ===== SCROLLBAR ===== */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: rgba(255,255,255,0.15); border-radius: 3px; }

/* ===== NAV ===== */
#nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 2rem;
  height: 56px;
  background: rgba(8,11,20,0.85);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
  transition: all 0.3s;
}

.nav-logo {
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text2);
  font-family: var(--mono);
}

.nav-links {
  display: flex;
  gap: 0.25rem;
}

.nav-link {
  color: var(--text2);
  text-decoration: none;
  font-size: 0.8rem;
  font-weight: 500;
  padding: 0.35rem 0.85rem;
  border-radius: 6px;
  transition: all 0.2s;
  letter-spacing: 0.02em;
}

.nav-link:hover {
  color: var(--text);
  background: var(--surface2);
}

/* ===== HERO ===== */
#hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

#hero-canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  opacity: 0.35;
}

.hero-content {
  position: relative;
  z-index: 1;
  text-align: center;
  max-width: 900px;
  padding: 6rem 2rem 4rem;
}

.hero-badge {
  display: inline-block;
  font-family: var(--mono);
  font-size: 0.72rem;
  font-weight: 500;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: #8b5cf6;
  background: rgba(139,92,246,0.12);
  border: 1px solid rgba(139,92,246,0.25);
  padding: 0.3rem 0.9rem;
  border-radius: 20px;
  margin-bottom: 1.5rem;
}

.hero-title {
  font-size: clamp(2.4rem, 6vw, 4.2rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.1;
  margin-bottom: 1.2rem;
  background: linear-gradient(135deg, #ffffff 30%, #94a3b8 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: 1.05rem;
  color: var(--text2);
  max-width: 600px;
  margin: 0 auto 3rem;
  line-height: 1.7;
}

.hero-cards {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1rem;
  max-width: 800px;
  margin: 0 auto;
}

.hero-card {
  text-decoration: none;
  background: rgba(255,255,255,0.03);
  border: 1px solid rgba(255,255,255,0.07);
  border-top: 2px solid var(--c);
  border-radius: 12px;
  padding: 1.2rem 1rem;
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
  transition: all 0.25s cubic-bezier(0.4,0,0.2,1);
  cursor: pointer;
}

.hero-card:hover {
  background: rgba(255,255,255,0.06);
  transform: translateY(-3px);
  box-shadow: 0 8px 32px rgba(0,0,0,0.4), 0 0 0 1px rgba(255,255,255,0.08);
}

.hero-card-num {
  font-family: var(--mono);
  font-size: 0.68rem;
  color: var(--c);
  font-weight: 500;
}

.hero-card-title {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.01em;
}

.hero-card-desc {
  font-size: 0.75rem;
  color: var(--text3);
  line-height: 1.4;
}

/* ===== EXPERIMENT SECTIONS ===== */
.experiment-section {
  padding: 5rem 0 6rem;
  border-top: 1px solid var(--border);
  position: relative;
}

.experiment-section::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--c-section, #8b5cf6), transparent);
  opacity: 0.5;
}

.section-inner {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 2rem;
}

.section-header {
  margin-bottom: 2.5rem;
}

.section-badge {
  display: inline-block;
  font-family: var(--mono);
  font-size: 0.68rem;
  font-weight: 500;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--c);
  background: rgba(0,0,0,0.3);
  border: 1px solid rgba(255,255,255,0.1);
  padding: 0.25rem 0.75rem;
  border-radius: 20px;
  margin-bottom: 1rem;
}

.section-title {
  font-size: clamp(1.6rem, 3.5vw, 2.4rem);
  font-weight: 800;
  letter-spacing: -0.025em;
  line-height: 1.15;
  margin-bottom: 1rem;
  color: #f1f5f9;
}

.section-claim {
  font-size: 1rem;
  color: var(--text2);
  max-width: 680px;
  line-height: 1.75;
}

.section-claim strong {
  color: var(--text);
  font-weight: 600;
}

.section-claim em {
  color: var(--text);
  font-style: normal;
  font-weight: 500;
}

/* ===== CONTROLS ===== */
.experiment-controls {
  display: flex;
  align-items: center;
  gap: 1.5rem;
  flex-wrap: wrap;
  margin-bottom: 2rem;
}

.btn-run {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: var(--c);
  color: white;
  border: none;
  border-radius: 8px;
  padding: 0.6rem 1.4rem;
  font-size: 0.88rem;
  font-weight: 600;
  font-family: var(--sans);
  cursor: pointer;
  transition: all 0.2s;
  letter-spacing: 0.01em;
  position: relative;
  overflow: hidden;
}

.btn-run::after {
  content: '';
  position: absolute;
  inset: 0;
  background: rgba(255,255,255,0.1);
  opacity: 0;
  transition: opacity 0.2s;
}

.btn-run:hover::after { opacity: 1; }
.btn-run:active { transform: scale(0.97); }

.btn-run:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.btn-icon { font-size: 0.75rem; }

.stat-row {
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
  align-items: center;
}

.stat-badge {
  background: rgba(0,0,0,0.3);
  border: 1px solid rgba(255,255,255,0.08);
  border-left: 2px solid var(--c);
  border-radius: 6px;
  padding: 0.4rem 0.85rem;
  display: flex;
  flex-direction: column;
  gap: 0.1rem;
}

.stat-label {
  font-size: 0.65rem;
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text3);
  font-family: var(--mono);
}

.stat-val {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--text);
  font-family: var(--mono);
  transition: all 0.3s;
}

/* ===== CANVAS GRIDS ===== */
.canvas-grid-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.25rem;
  margin-bottom: 1.5rem;
}

.canvas-grid-3 {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.canvas-grid-3.small-canvases {
  margin-bottom: 1.25rem;
}

.canvas-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  overflow: hidden;
  transition: box-shadow 0.3s;
}

.canvas-card:hover {
  box-shadow: 0 0 0 1px rgba(255,255,255,0.08), 0 4px 24px rgba(0,0,0,0.3);
}

.canvas-card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--border);
}

.canvas-card-title {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text);
}

.canvas-card-tag {
  font-family: var(--mono);
  font-size: 0.65rem;
  color: var(--text3);
  background: rgba(255,255,255,0.04);
  padding: 0.15rem 0.5rem;
  border-radius: 4px;
  border: 1px solid var(--border);
}

.canvas-card canvas {
  display: block;
  width: 100%;
  height: auto;
}

.canvas-footer {
  padding: 0.6rem 1rem;
  border-top: 1px solid var(--border);
}

.progress-bar {
  height: 3px;
  background: rgba(255,255,255,0.06);
  border-radius: 2px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: var(--c);
  border-radius: 2px;
  transition: width 0.1s linear;
  box-shadow: 0 0 6px var(--c);
}

.canvas-card.wide { grid-column: span 1; }
.canvas-card.full-width-card { width: 100%; }

/* ===== LOSS CHART ===== */
.loss-chart-wrap {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  overflow: hidden;
  margin-bottom: 1.5rem;
  padding: 0.5rem;
}

.loss-chart-wrap canvas {
  display: block;
  width: 100%;
  height: auto;
}

/* ===== INSIGHT BOX ===== */
.insight-box {
  display: flex;
  gap: 1rem;
  background: rgba(0,0,0,0.25);
  border: 1px solid rgba(255,255,255,0.06);
  border-left: 3px solid var(--c);
  border-radius: 10px;
  padding: 1.1rem 1.3rem;
  margin-top: 1.5rem;
}

.insight-icon {
  font-size: 1.1rem;
  flex-shrink: 0;
  margin-top: 0.1rem;
}

.insight-text {
  font-size: 0.87rem;
  color: var(--text2);
  line-height: 1.7;
}

.insight-text strong {
  color: var(--text);
  font-weight: 600;
}

/* ===== S1-2 MATRIX COLLAPSE ===== */
.matrix-collapse-box {
  background: rgba(0,0,0,0.3);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
  margin-bottom: 1.5rem;
  text-align: center;
}

.matrix-collapse-title {
  font-size: 1rem;
  font-weight: 700;
  font-family: var(--mono);
  margin-bottom: 1rem;
  letter-spacing: 0.02em;
}

.matrix-equation {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  flex-wrap: wrap;
  margin-bottom: 0.75rem;
}

.matrix-block {
  background: rgba(255,255,255,0.04);
  border: 1px solid rgba(255,255,255,0.1);
  border-radius: 6px;
  padding: 0.5rem 0.75rem;
  font-family: var(--mono);
  font-size: 0.72rem;
  color: var(--text2);
}

.matrix-op {
  color: var(--text3);
  font-family: var(--mono);
  font-size: 0.9rem;
}

.matrix-note {
  font-size: 0.78rem;
  color: var(--text3);
}

/* ===== S1-3 VOCAB ===== */
.vocab-display {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
  margin-bottom: 2rem;
}

.vocab-group {
  background: var(--surface);
  border: 1px solid var(--border);
  border-top: 2px solid var(--c);
  border-radius: 10px;
  padding: 0.75rem 1rem;
  flex: 1;
  min-width: 140px;
}

.vocab-label {
  font-size: 0.65rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--c);
  display: block;
  margin-bottom: 0.5rem;
  font-family: var(--mono);
}

.vocab-tokens {
  display: flex;
  gap: 0.4rem;
  flex-wrap: wrap;
}

.token {
  font-family: var(--mono);
  font-size: 0.75rem;
  background: rgba(255,255,255,0.06);
  border: 1px solid rgba(255,255,255,0.1);
  color: var(--text);
  padding: 0.2rem 0.6rem;
  border-radius: 5px;
}

.token-template {
  color: var(--text2);
}

/* ===== EMBEDDING LAYOUT ===== */
.embedding-layout {
  display: grid;
  grid-template-columns: 1fr 280px;
  gap: 1.25rem;
  margin-bottom: 1.5rem;
}

.embedding-sidebar {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.neighbors-list {
  padding: 0.75rem;
  min-height: 120px;
}

.neighbors-placeholder {
  font-size: 0.78rem;
  color: var(--text3);
  text-align: center;
  padding: 1rem;
}

.neighbor-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.4rem 0;
  border-bottom: 1px solid var(--border);
  font-size: 0.78rem;
}

.neighbor-item:last-child { border-bottom: none; }

.neighbor-token {
  font-family: var(--mono);
  color: var(--text);
  font-weight: 500;
}

.neighbor-sim {
  font-family: var(--mono);
  color: var(--text3);
  font-size: 0.7rem;
}

.neighbor-cat {
  font-size: 0.65rem;
  padding: 0.1rem 0.4rem;
  border-radius: 4px;
  font-weight: 600;
  font-family: var(--mono);
}

/* ===== S1-4 GENERALIZATION ===== */
.generalization-layout {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.chart-legend {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 0.5rem 1rem 0.75rem;
  flex-wrap: wrap;
}

.legend-item {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.75rem;
  color: var(--text2);
}

.legend-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  flex-shrink: 0;
}

.legend-note {
  font-size: 0.68rem;
  color: var(--text3);
  font-family: var(--mono);
  margin-left: auto;
}

/* ===== FOOTER ===== */
footer {
  border-top: 1px solid var(--border);
  padding: 2.5rem;
  text-align: center;
}

.footer-text {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text2);
  letter-spacing: 0.04em;
  margin-bottom: 0.4rem;
}

.footer-sub {
  font-size: 0.75rem;
  color: var(--text3);
  font-family: var(--mono);
}

/* ===== ANIMATIONS ===== */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(24px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}

.animate-in {
  animation: fadeInUp 0.6s cubic-bezier(0.4,0,0.2,1) both;
}

.section-header { animation: fadeInUp 0.5s 0.1s both; }

/* ===== RESPONSIVE ===== */
@media (max-width: 720px) {
  .hero-cards { grid-template-columns: 1fr 1fr; }
  .canvas-grid-2 { grid-template-columns: 1fr; }
  .canvas-grid-3 { grid-template-columns: 1fr; }
  .embedding-layout { grid-template-columns: 1fr; }
  .nav-links { display: none; }
  .section-inner { padding: 0 1rem; }
  .hero-content { padding: 5rem 1rem 3rem; }
}