/* ---------- root ---------- */
:root {
  --bg-0:        #ffffff;
  --bg-1:        #f7f8fb;
  --bg-2:        #eef0f5;
  --line:        rgba(15,20,40,0.08);
  --line-strong: rgba(15,20,40,0.18);
  --fg-0:        #0e1320;
  --fg-1:        #3a4256;
  --fg-2:        #6b7388;
  --accent:      #2f6fe5;
  --accent-2:    #7c5cd8;
  --ours:        #128a64;
  --shadow:      0 6px 24px rgba(15,20,40,0.08);
  --radius:      14px;
  --font-sans:   "Inter", "SF Pro Text", "Helvetica Neue", system-ui, sans-serif;
  --font-mono:   "JetBrains Mono", "SF Mono", ui-monospace, monospace;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }

body {
  background:
    radial-gradient(1200px 600px at 80% -10%, rgba(47,111,229,0.06), transparent 60%),
    radial-gradient(900px  600px at -10% 30%, rgba(124,92,216,0.05), transparent 60%),
    var(--bg-0);
  color: var(--fg-0);
  font-family: var(--font-sans);
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ---------- nav ---------- */
.nav {
  position: sticky;
  top: 0;
  z-index: 50;
  backdrop-filter: blur(14px);
  background: rgba(255,255,255,0.78);
  border-bottom: 1px solid var(--line);
}
.nav-inner {
  max-width: 1240px;
  margin: 0 auto;
  padding: 14px 32px;
  display: flex;
  align-items: center;
  gap: 24px;
}
.nav-brand {
  font-weight: 700;
  letter-spacing: 0.5px;
  font-size: 14px;
  color: var(--fg-0);
}
.nav-brand .accent {
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.nav-links { display: flex; gap: 18px; flex: 1; flex-wrap: wrap; }
.nav-links a {
  color: var(--fg-1);
  font-size: 13px;
  padding: 6px 10px;
  border-radius: 8px;
  border: 1px solid transparent;
}
.nav-links a:hover {
  color: var(--fg-0);
  border-color: var(--line-strong);
  background: rgba(15,20,40,0.04);
  text-decoration: none;
}

/* ---------- hero ---------- */
.hero {
  max-width: 1240px;
  margin: 0 auto;
  padding: 72px 32px 40px;
}
.hero h1 {
  font-size: clamp(28px, 4vw, 52px);
  line-height: 1.1;
  margin: 0 0 20px;
  font-weight: 800;
  letter-spacing: -0.02em;
}
.hero h1 .grad {
  background: linear-gradient(120deg, #0e1320 0%, #2f6fe5 55%, #7c5cd8 95%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.hero .subtitle {
  max-width: 920px;
  font-size: clamp(15px, 1.3vw, 17px);
  color: var(--fg-1);
  margin: 0 0 28px;
}
.hero-meta {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}
.pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 12px;
  padding: 6px 12px;
  border-radius: 999px;
  border: 1px solid var(--line-strong);
  color: var(--fg-1);
  background: rgba(15,20,40,0.02);
}
.pill.accent {
  border-color: rgba(47,111,229,0.45);
  color: #1f4cb0;
  background: rgba(47,111,229,0.08);
}

/* ---------- sections ---------- */
section.section {
  max-width: 1240px;
  margin: 0 auto;
  padding: 56px 32px;
  border-top: 1px solid var(--line);
}
.section-head {
  margin-bottom: 28px;
  position: relative;
}
.section-toggle {
  position: absolute;
  top: 0;
  right: 0;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.5px;
  padding: 8px 14px;
  border-radius: 999px;
  border: 1px solid var(--line-strong);
  background: #fff;
  color: var(--fg-1);
  cursor: pointer;
  transition: all 0.15s ease;
  box-shadow: 0 1px 2px rgba(15,20,40,0.04);
}
.section-toggle:hover {
  border-color: var(--accent);
  color: var(--accent);
}
.section-toggle .icon {
  font-size: 11px;
  width: 12px;
  text-align: center;
  color: var(--accent);
}
.section-toggle[data-state="paused"] {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}
.section-toggle[data-state="paused"] .icon { color: #fff; }
@media (max-width: 600px) {
  .section-toggle { position: static; margin-bottom: 12px; }
}
.section-eyebrow {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--accent);
  letter-spacing: 2px;
  text-transform: uppercase;
}
.section-head h2 {
  margin: 6px 0 8px;
  font-size: clamp(22px, 2.6vw, 32px);
  letter-spacing: -0.01em;
}
.section-head p {
  color: var(--fg-1);
  max-width: 920px;
  margin: 0;
}

/* ---------- shared video card ---------- */
.scene-block {
  background: var(--bg-0);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px;
  margin-bottom: 22px;
  box-shadow: var(--shadow);
}
.scene-block-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 14px;
  flex-wrap: wrap;
}
.scene-block-header h3 { flex: 1; }
.block-toggle {
  position: static !important;
  font-size: 11px;
  padding: 6px 12px;
}
.block-toggle .icon { font-size: 10px; }
.scene-block-header h3 {
  margin: 0;
  font-size: 15px;
  font-weight: 600;
  letter-spacing: 0.2px;
}
.scene-block-header .tag {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--fg-2);
}

/* swipe wrapper: reveals LiDAR underneath */
.video-card {
  position: relative;
  border-radius: 10px;
  overflow: hidden;
  background: #000;
  aspect-ratio: 16 / 9;
  border: 1px solid var(--line);
}
.video-card.taller { aspect-ratio: 16 / 9; }
.video-card video {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}
/* Last-frame overlay used to mask the brief black flash when src swaps. */
.video-card .swap-overlay {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  z-index: 2;
  pointer-events: none;
  display: none;
}
.video-card .label {
  position: absolute;
  top: 8px; left: 8px;
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.5px;
  text-transform: uppercase;
  background: rgba(0,0,0,0.62);
  border: 1px solid rgba(255,255,255,0.18);
  color: #fff;
  padding: 4px 8px;
  border-radius: 6px;
  z-index: 4;
  pointer-events: none;
}
.video-card .label.ours {
  background: rgba(18,138,100,0.85);
  border-color: rgba(255,255,255,0.25);
  color: #fff;
}
.video-card .label.lidar {
  background: rgba(124,92,216,0.85);
  border-color: rgba(255,255,255,0.25);
  color: #fff;
}
/* Red label for the two "extreme" out-of-distribution trajectories in §1. */
.video-card .label.extreme {
  background: rgba(214,46,46,0.92);
  border-color: rgba(255,255,255,0.25);
  color: #fff;
}
/* Inline word-level highlight matching the .label.extreme colour. */
.extreme-text {
  color: #d62e2e;
  font-weight: 600;
}
.video-card .hint {
  position: absolute;
  bottom: 8px; right: 10px;
  font-family: var(--font-mono);
  font-size: 10px;
  color: var(--fg-2);
  background: rgba(0,0,0,0.45);
  padding: 3px 7px;
  border-radius: 5px;
  z-index: 4;
  pointer-events: none;
}

/* swipe mechanics: bottom layer is LiDAR; top layer is generated, clipped */
.video-card.swipe .bottom { z-index: 1; }
.video-card.swipe .top {
  z-index: 2;
  clip-path: inset(0 var(--swipe-right, 0%) 0 0);
}
.video-card.swipe .swipe-handle {
  position: absolute;
  top: 0; bottom: 0;
  left: var(--swipe-pos, 100%);
  width: 2px;
  background: linear-gradient(180deg, var(--accent), var(--accent-2));
  z-index: 3;
  pointer-events: none;
  box-shadow: 0 0 12px rgba(110,168,255,0.6);
}
.video-card.swipe .swipe-knob {
  position: absolute;
  top: 50%;
  left: var(--swipe-pos, 100%);
  width: 28px;
  height: 28px;
  margin-left: -14px;
  margin-top: -14px;
  border-radius: 50%;
  background: #fff;
  border: 2px solid var(--accent);
  z-index: 3;
  pointer-events: none;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 12px;
  color: var(--accent);
  box-shadow: 0 2px 12px rgba(15,20,40,0.25);
}
.video-card.swipe .swipe-track {
  position: absolute;
  inset: 0;
  z-index: 5;
  cursor: ew-resize;
  background: transparent;
}
/* readouts */
.video-card.swipe .swipe-side {
  position: absolute;
  bottom: 8px;
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.5px;
  padding: 3px 7px;
  border-radius: 5px;
  z-index: 4;
  pointer-events: none;
  background: rgba(0,0,0,0.55);
}
.video-card.swipe .swipe-side.left  { left: 8px;  color: #fff; }
.video-card.swipe .swipe-side.right { right: 8px; color: #fff; }


/* ---------- section 1 layout: 2×4 grid (input + 7 trajectory tiles) ---------- */
.novel-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-auto-rows: 1fr;
  gap: 10px;
  margin: 0 auto 16px;
  max-width: 1560px;       /* 4 × 385 + 3 × 10 gap = 1570 ≈ 1560 */
}
.novel-input-card {
  /* Input is just a regular tile sitting at cell (1, 1); no row span. */
  width: 100%;
}
@media (max-width: 1100px) {
  .novel-grid {
    grid-template-columns: repeat(2, 1fr);
    max-width: 820px;
  }
}
@media (max-width: 600px) {
  .novel-grid {
    grid-template-columns: 1fr;
    max-width: 480px;
  }
}

/* ---------- section 2/3 layout: 2-3-3 grid ---------- */
.compare-block .row {
  display: grid;
  gap: 12px;
  margin-bottom: 12px;
}
.compare-block .row.row-2 { grid-template-columns: repeat(2, 1fr); max-width: 66.666%; margin-left: auto; margin-right: auto; }
.compare-block .row.row-3 { grid-template-columns: repeat(3, 1fr); }
@media (max-width: 900px) {
  .compare-block .row.row-2,
  .compare-block .row.row-3 { grid-template-columns: 1fr 1fr; max-width: none; }
}
@media (max-width: 560px) {
  .compare-block .row.row-2,
  .compare-block .row.row-3 { grid-template-columns: 1fr; }
}

/* ablation: 3-column 2-row grid (Lidar | GT | Full / w-cam | w-proj | w/o-ref) */
.grid-2x3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
}
@media (max-width: 700px) {
  .grid-2x3 { grid-template-columns: repeat(2, 1fr); }
}


/* ---------- section 2 baselines (single-grid controller) ---------- */
.baseline-note {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--fg-2);
  margin-bottom: 12px;
  letter-spacing: 0.3px;
}
/* §2 baseline grid: full-width 1×4 row (LiDAR · Baseline · Ours · GT). */
.baseline-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
  margin-bottom: 16px;
}
@media (max-width: 1100px) {
  .baseline-grid { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 600px) {
  .baseline-grid { grid-template-columns: 1fr; }
}

/* §5 novel-view-vs-baseline grid: 1×3 (Input · StreetCrafter* · Ours).
 * Capped to match the §3 tile width. */
.nvc-grid {
  grid-template-columns: repeat(3, 1fr) !important;
  max-width: 1170px;
}
@media (max-width: 1100px) {
  .nvc-grid { grid-template-columns: repeat(2, 1fr) !important; max-width: none; }
}
@media (max-width: 600px) {
  .nvc-grid { grid-template-columns: 1fr !important; }
}

/* §4 sparsity grid: full-width 1×4 row (GT · LiDAR · SC* · StreetNVS). */
.sparsity-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
  margin-bottom: 16px;
}
@media (max-width: 1100px) {
  .sparsity-grid { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 600px) {
  .sparsity-grid { grid-template-columns: 1fr; }
}

/* ---------- section 4 sparsity ---------- */
.sparsity-controls {
  display: flex;
  flex-wrap: wrap;
  gap: 18px;
  align-items: center;
  background: var(--bg-1);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 16px 20px;
  margin-bottom: 18px;
}
.sparsity-controls label {
  font-size: 12px;
  letter-spacing: 0.5px;
  color: var(--fg-2);
  font-family: var(--font-mono);
  text-transform: uppercase;
  margin-right: 8px;
}
.sparsity-controls .scene-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}
.sparsity-controls .scene-buttons button {
  padding: 7px 12px;
  font-size: 12px;
  font-family: var(--font-mono);
  background: #fff;
  color: var(--fg-1);
  border: 1px solid var(--line-strong);
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.15s ease;
}
.sparsity-controls .scene-buttons button:hover {
  background: rgba(47,111,229,0.06);
  color: var(--fg-0);
}
.sparsity-controls .scene-buttons button.active {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}
/* .sparsity-grid layout is defined alongside .baseline-grid above. */

.density-slider {
  background: var(--bg-1);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px 24px 22px;
}
.density-slider .header {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  margin-bottom: 14px;
  flex-wrap: wrap;
  gap: 8px;
}
.density-slider .header .title {
  font-size: 13px;
  font-family: var(--font-mono);
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--fg-2);
}
.density-slider .header .value {
  font-family: var(--font-mono);
  color: var(--accent);
  font-size: 14px;
}
.density-slider .track {
  position: relative;
  height: 36px;
  display: flex;
  align-items: center;
}
.density-slider input[type="range"] {
  width: 100%;
  appearance: none;
  height: 6px;
  background: linear-gradient(90deg, rgba(47,111,229,0.18), rgba(124,92,216,0.5));
  border-radius: 999px;
  outline: none;
  border: 1px solid var(--line-strong);
}
.density-slider input[type="range"]::-webkit-slider-thumb {
  appearance: none;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  border: 2px solid #fff;
  cursor: pointer;
  box-shadow: 0 2px 10px rgba(15,20,40,0.18);
}
.density-slider input[type="range"]::-moz-range-thumb {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  border: 2px solid #fff;
  cursor: pointer;
}
.density-slider .ticks {
  display: flex;
  justify-content: space-between;
  margin-top: 8px;
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--fg-2);
}
.density-slider .ticks span { cursor: pointer; padding: 4px 8px; border-radius: 6px; }
.density-slider .ticks span:hover { background: rgba(47,111,229,0.08); color: var(--fg-0); }
.density-slider .ticks span.active { color: var(--accent); font-weight: 600; }


/* ---------- footer ---------- */
footer {
  max-width: 1240px;
  margin: 0 auto;
  padding: 40px 32px 60px;
  border-top: 1px solid var(--line);
  color: var(--fg-2);
  font-size: 12px;
  text-align: center;
}