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

:root {
  /* Pure white foundation */
  --bg-main: #ffffff;
  --bg-alt: #ffffff;
  --bg-hero: #ffffff;

  /* Card & border system */
  --card-bg: #ffffff;
  --card-border: #e8e8e8;
  --card-hover-border: #d0d0d0;
  --card-shadow: 0 1px 3px rgba(0,0,0,0.04), 0 6px 24px rgba(0,0,0,0.06);
  --card-shadow-hover: 0 2px 8px rgba(0,0,0,0.06), 0 12px 36px rgba(0,0,0,0.10);

  /* Accent — deep indigo-slate */
  --accent: #2d3748;
  --accent-soft: #4a5568;
  --accent-tint: #edf2f7;
  --accent-blue: #3b82f6;
  --accent-blue-soft: #dbeafe;

  /* Tag palette — sophisticated muted */
  --tag-p: #0d9488;
  --tag-p-bg: #f0fdfa;
  --tag-p-border: #99f6e4;
  --tag-g: #7c3aed;
  --tag-g-bg: #f5f3ff;
  --tag-g-border: #c4b5fd;
  --tag-e: #ea580c;
  --tag-e-bg: #fff7ed;
  --tag-e-border: #fed7aa;

  /* Text hierarchy */
  --text-primary: #111827;
  --text-secondary: #6b7280;
  --text-muted: #9ca3af;
  --text-faint: #d1d5db;

  /* Geometry */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;

  --transition: 0.2s ease;
  --font: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', monospace;
}

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

a {
  color: var(--accent-blue);
  text-decoration: none;
  transition: color var(--transition);
}
a:hover { color: #2563eb; }

/* ===== CONTAINER ===== */
.container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 2rem;
}

/* ===== NAVBAR ===== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  padding: 0.75rem 0;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid transparent;
  transition: all var(--transition);
}

.navbar.scrolled {
  padding: 0.5rem 0;
  border-bottom-color: var(--card-border);
  box-shadow: 0 1px 8px rgba(0,0,0,0.04);
}

.nav-inner {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 2rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-logo {
  font-size: 1.2rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  color: var(--text-primary);
}

.nav-links {
  display: flex;
  gap: 0.125rem;
}

.nav-links a {
  color: var(--text-secondary);
  font-size: 0.82rem;
  font-weight: 500;
  padding: 0.4rem 0.7rem;
  border-radius: var(--radius-sm);
  transition: all var(--transition);
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--text-primary);
  background: var(--accent-tint);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}
.nav-toggle span {
  display: block;
  width: 20px;
  height: 1.5px;
  background: var(--text-secondary);
  border-radius: 2px;
  transition: var(--transition);
}

/* ===== HERO ===== */
.hero {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  position: relative;
  padding: 6rem 2rem 4rem;
  background: var(--bg-hero);
}

.hero-content {
  position: relative;
  z-index: 1;
  max-width: 1100px;
  width: 100%;
}

.hero-title {
  font-size: clamp(2rem, 4.5vw, 3.2rem);
  font-weight: 800;
  line-height: 1.12;
  letter-spacing: -0.035em;
  margin-bottom: 1rem;
  color: var(--text-primary);
}

.title-accent {
  background: linear-gradient(135deg, #3b82f6, #8b5cf6);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: 1.15rem;
  color: var(--text-secondary);
  font-weight: 400;
  margin-bottom: 2rem;
  letter-spacing: -0.01em;
}

.hero-authors {
  margin-bottom: 1.5rem;
  max-width: 800px;
  margin-left: auto;
  margin-right: auto;
}

.author-list {
  font-size: 1rem;
  color: var(--text-primary);
  line-height: 1.8;
  margin-bottom: 0.5rem;
}

.author {
  white-space: nowrap;
  color: var(--text-primary);
  text-decoration: none;
  transition: color 0.2s;
}

a.author:hover {
  color: var(--accent);
}

.author sup {
  color: var(--accent);
  font-weight: 600;
}

.institution-list {
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.8;
}

.institution-list sup {
  color: var(--accent);
  font-weight: 600;
}

.hero-actions {
  display: flex;
  gap: 1.5rem;
  justify-content: center;
}

/* ===== BUTTONS ===== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.65rem 1.5rem;
  border-radius: var(--radius-sm);
  font-family: var(--font);
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  border: none;
  transition: all var(--transition);
}
.btn-primary {
  background: var(--text-primary);
  color: #fff;
}
.btn-primary:hover {
  background: #000;
  color: #fff;
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(0,0,0,0.15);
}
.btn-ghost {
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--card-border);
}
.btn-ghost:hover {
  background: var(--accent-tint);
  color: var(--text-primary);
  border-color: var(--card-hover-border);
}
.btn-outline {
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--card-border);
  font-size: 0.95rem;
  padding: 0.55rem 1.25rem;
  margin-top: 1rem;
}
.btn-outline:hover {
  background: var(--accent-tint);
  color: var(--text-primary);
}

/* ===== SCROLL INDICATOR ===== */
.scroll-indicator {
  position: absolute;
  bottom: 2rem;
  left: 50%;
  transform: translateX(-50%);
}
.scroll-arrow {
  width: 20px;
  height: 20px;
  border-right: 1.5px solid var(--text-faint);
  border-bottom: 1.5px solid var(--text-faint);
  transform: rotate(45deg);
  animation: scrollBounce 2s infinite;
}
@keyframes scrollBounce {
  0%, 100% { transform: rotate(45deg) translate(0, 0); opacity: 0.4; }
  50% { transform: rotate(45deg) translate(4px, 4px); opacity: 0.8; }
}

/* ===== SECTIONS ===== */
.section {
  padding: 5rem 0;
  position: relative;
  background: var(--bg-main);
}
.section-alt {
  background: var(--bg-alt);
}
/* Thin top divider for alternating sections */
.section + .section {
  border-top: 1px solid #f0f0f0;
}

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

.section-label {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent-blue);
  background: var(--accent-blue-soft);
  padding: 0.25rem 0.85rem;
  border-radius: 100px;
  margin-bottom: 0.75rem;
}

.section-title {
  font-size: clamp(1.75rem, 3.5vw, 2.5rem);
  font-weight: 800;
  letter-spacing: -0.025em;
  margin-bottom: 0.5rem;
  color: var(--text-primary);
}

.section-desc {
  font-size: 1rem;
  color: var(--text-secondary);
  max-width: 760px;
  margin: 0 auto;
  line-height: 1.6;
}

.carousel-hint {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  margin-top: 0.6rem;
  font-size: 0.78rem;
  color: var(--text-muted);
  font-weight: 400;
  letter-spacing: 0.01em;
}
.carousel-hint svg {
  opacity: 0.5;
}

/* ===== GLASS CARDS ===== */
.glass-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  box-shadow: var(--card-shadow);
  transition: all var(--transition);
}
.glass-card:hover {
  border-color: var(--card-hover-border);
  box-shadow: var(--card-shadow-hover);
}

/* ===== OVERVIEW GRID ===== */
.overview-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.25rem;
  margin-bottom: 1.5rem;
}

.overview-card {
  text-align: center;
  padding: 2rem 1.25rem;
}
.overview-card h3 {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 0.4rem;
  color: var(--text-primary);
}
.overview-card p {
  font-size: 0.88rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

.op-icon {
  width: 52px;
  height: 52px;
  border-radius: 14px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 0.85rem;
}
.op-p {
  background: var(--tag-p-bg);
  color: var(--tag-p);
  border: 1px solid var(--tag-p-border);
}
.op-g {
  background: var(--tag-g-bg);
  color: var(--tag-g);
  border: 1px solid var(--tag-g-border);
}
.op-e {
  background: var(--tag-e-bg);
  color: var(--tag-e);
  border: 1px solid var(--tag-e-border);
}

/* ===== HERO FIGURES (teaser + radar side by side) ===== */
.hero-figures {
  margin-top: 3rem;
  max-width: 1400px;
  width: 100%;
  display: flex;
  align-items: stretch;
  gap: 1.25rem;
}
.hero-fig-item {
  border-radius: var(--radius-lg);
  border: 1px solid var(--card-border);
  box-shadow: var(--card-shadow);
  overflow: hidden;
  display: flex;
  align-items: center;
  background: #fff;
}
.hero-fig-item img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  display: block;
}
.hero-fig-teaser {
  flex: 1.8;
}
.hero-fig-radar {
  flex: 1;
}
@media (max-width: 768px) {
  .hero-figures {
    flex-direction: column;
  }
}

/* ===== SECTION FIGURES ===== */
.section-figure {
  width: 100%;
  height: auto;
  border-radius: var(--radius-md);
}

.overview-detail {
  text-align: center;
  padding: 1.5rem 2.5rem;
}
.overview-detail p {
  font-size: 1rem;
  color: var(--text-secondary);
  line-height: 1.7;
}
.overview-detail strong {
  color: var(--text-primary);
}

/* ===== FIGURE / VIDEO PLACEHOLDERS ===== */
.figure-placeholder,
.video-placeholder {
  background: #fafafa;
  border: 1px solid var(--card-border);
  border-radius: var(--radius-md);
  aspect-ratio: 4 / 3;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
  cursor: pointer;
  transition: all var(--transition);
}

.figure-placeholder {
  margin-top: 1.5rem;
}

.video-placeholder:hover {
  border-color: var(--accent-blue);
  background: #f8faff;
}
.video-placeholder.small {
  aspect-ratio: 16 / 9;
}

.video-placeholder video {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  border-radius: var(--radius-md);
}

.video-placeholder.has-video .placeholder-inner {
  display: none;
}

.placeholder-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.4rem;
  color: var(--text-muted);
}
.placeholder-inner span {
  font-size: 0.82rem;
  font-weight: 500;
}
.placeholder-inner small {
  font-size: 0.72rem;
  opacity: 0.6;
}

/* ===== DEMO BLOCKS ===== */
.demo-block {
  margin-bottom: 1.5rem;
}
.demo-block:last-child {
  margin-bottom: 0;
}

.demo-prompt {
  display: flex;
  align-items: flex-start;
  gap: 0.65rem;
  padding: 0.85rem 1.1rem;
  background: #f8faff;
  border: 1px solid #e0e7ff;
  border-radius: var(--radius-md);
  margin-bottom: 1.25rem;
  font-size: 0.92rem;
  color: var(--text-primary);
  line-height: 1.5;
}
.demo-prompt svg {
  flex-shrink: 0;
  color: var(--accent-blue);
  margin-top: 2px;
}

/* ===== COMPARISON TABS ===== */
.tab-buttons {
  display: flex;
  gap: 2px;
  padding: 3px;
  background: #f4f4f5;
  border-radius: var(--radius-md);
  margin-bottom: 1rem;
  overflow-x: auto;
}

.tab-btn {
  flex: 1;
  padding: 0.5rem 0.85rem;
  background: transparent;
  border: none;
  border-radius: calc(var(--radius-md) - 3px);
  color: var(--text-secondary);
  font-family: var(--font);
  font-size: 0.82rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition);
  white-space: nowrap;
}
.tab-btn:hover {
  color: var(--text-primary);
}
.tab-btn.active {
  background: #ffffff;
  color: var(--text-primary);
  box-shadow: 0 1px 3px rgba(0,0,0,0.08);
}

.tab-panels {
  position: relative;
}
.tab-panel {
  display: none;
  animation: fadeIn 0.25s ease;
}
.tab-panel.active {
  display: block;
}
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ===== COMPARISON GRIDS ===== */
/* ===== TEXT-TO-MOTION GRID ===== */
.t2m-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.2rem;
}
.t2m-grid-2 {
  grid-template-columns: repeat(2, 1fr);
}
.t2m-item {
  text-align: center;
  display: flex;
  flex-direction: column;
}
.t2m-prompt {
  font-size: 0.85rem;
  color: var(--text-secondary);
  font-style: italic;
  margin-bottom: 0.6rem;
  line-height: 1.4;
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* ===== INPAINTING LEGEND ===== */
.inpainting-legend {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-top: 0.5rem;
}
.legend-dot {
  display: inline-block;
  width: 12px;
  height: 12px;
  border-radius: 50%;
}

/* ===== INPAINTING GALLERY ===== */
.inpainting-gallery {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}
.inpainting-section {
  padding: 1.2rem 1.5rem 1.5rem;
}
.inpainting-heading {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  text-align: center;
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--card-border);
}

.comparison-grid {
  display: grid;
  gap: 1rem;
}
.comparison-grid-3 { grid-template-columns: repeat(3, 1fr); }
.comparison-grid-4 { grid-template-columns: repeat(4, 1fr); }

/* Ablation: 2x2 panel */
.ablation-grid-2x2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1rem;
}

/* Ablation: src + 2x2 panel (motionfix editing) */
.ablation-src-panel {
  display: grid;
  grid-template-columns: 1fr 2fr;
  gap: 1.2rem;
  align-items: center;
}
.ablation-src-center {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
}
.ablation-src-center .video-placeholder {
  width: 100%;
}

/* Ablation sub-section headings */
.ablation-gallery {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}
.ablation-section {
  padding: 1.2rem 1.5rem 1.5rem;
}
.ablation-heading {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  text-align: center;
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--card-border);
}

.grid-item {
  text-align: center;
}
.grid-label {
  margin-top: 0.6rem;
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text-secondary);
}
.grid-label small {
  display: block;
  color: var(--text-muted);
  font-weight: 400;
  margin-top: 0.15rem;
}

/* Grid view for tab-based comparisons */
.comparison-tabs.grid-view .tab-panels {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1rem;
}
.comparison-tabs.grid-view .tab-panel {
  display: block;
}
.comparison-tabs.grid-view .tab-panel::before {
  content: attr(data-panel);
  display: block;
  text-align: center;
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--text-secondary);
  margin-bottom: 0.4rem;
  text-transform: capitalize;
}
.comparison-tabs.grid-view .tab-buttons {
  display: none;
}

/* ===== SUBTASK TABS ===== */
.subtask-tabs {
  display: flex;
  gap: 0.4rem;
  justify-content: center;
  margin-bottom: 2rem;
  flex-wrap: wrap;
}

.subtask-btn {
  padding: 0.5rem 1.25rem;
  background: transparent;
  border: 1px solid var(--card-border);
  border-radius: 100px;
  color: var(--text-secondary);
  font-family: var(--font);
  font-size: 0.82rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition);
}
.subtask-btn:hover {
  border-color: var(--card-hover-border);
  color: var(--text-primary);
}
.subtask-btn.active {
  background: var(--text-primary);
  border-color: var(--text-primary);
  color: #fff;
}

.subtask-panel {
  display: none;
  animation: fadeIn 0.25s ease;
}
.subtask-panel.active {
  display: block;
}

/* ===== EDIT COMPARISON ===== */
.edit-comparison {
  display: flex;
  align-items: center;
  gap: 1.25rem;
}
.edit-col {
  flex: 1;
}
.edit-col h4 {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 0.6rem;
  text-align: center;
}
.edit-arrow {
  flex-shrink: 0;
  color: var(--text-muted);
  opacity: 0.6;
}

/* ===== FOOTER ===== */
.footer {
  padding: 2.5rem 0;
  border-top: 1px solid #f0f0f0;
  text-align: center;
  background: #fff;
}
.footer-inner p {
  font-size: 0.85rem;
  color: var(--text-secondary);
}
.footer-note {
  margin-top: 0.4rem;
  font-size: 0.78rem;
  color: var(--text-muted);
}

/* ===== RESPONSIVE ===== */
@media (max-width: 1024px) {
  .overview-grid {
    grid-template-columns: repeat(3, 1fr);
    gap: 1rem;
  }
  .comparison-grid-4 {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 768px) {
  .nav-links { display: none; }
  .nav-toggle { display: flex; }

  .nav-links.open {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.98);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    padding: 0.75rem;
    border-bottom: 1px solid var(--card-border);
  }

  .hero { padding: 5rem 1.5rem 3rem; }
  .hero-title { font-size: 2rem; }
  .hero-actions { flex-direction: column; align-items: center; }

  .overview-grid {
    grid-template-columns: 1fr;
  }

  .comparison-grid-3,
  .comparison-grid-4 {
    grid-template-columns: repeat(2, 1fr);
  }
  .t2m-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  .ablation-src-panel {
    grid-template-columns: 1fr;
  }

  .edit-comparison {
    flex-direction: column;
  }
  .edit-arrow {
    transform: rotate(90deg);
  }

  .glass-card { padding: 1.25rem; }
  .overview-detail { padding: 1.25rem; }
  .section { padding: 3.5rem 0; }
  .container { padding: 0 1rem; }
}

@media (max-width: 480px) {
  .comparison-grid-3,
  .comparison-grid-4 {
    grid-template-columns: 1fr;
  }
  .t2m-grid {
    grid-template-columns: 1fr;
  }
  .subtask-tabs {
    flex-direction: column;
    align-items: center;
  }
}

/* ===== CAROUSEL ===== */
.carousel {
  position: relative;
  padding: 0 3rem;
}

.carousel-viewport {
  position: relative;
  overflow: hidden;
}

.carousel-slide {
  display: none;
  animation: carouselFadeIn 0.4s ease;
}

.carousel-slide.active {
  display: block;
}

@keyframes carouselFadeIn {
  from { opacity: 0; transform: translateX(24px); }
  to { opacity: 1; transform: translateX(0); }
}

.carousel-btn {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  width: 40px;
  height: 40px;
  border-radius: 50%;
  border: 1px solid var(--card-border);
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  color: var(--text-secondary);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition);
  box-shadow: 0 2px 8px rgba(0,0,0,0.08);
  z-index: 10;
}

.carousel-btn:hover {
  background: var(--text-primary);
  color: #fff;
  border-color: var(--text-primary);
  box-shadow: 0 4px 12px rgba(0,0,0,0.15);
}

.carousel-btn.disabled {
  opacity: 0.3;
  pointer-events: none;
}

.carousel-prev {
  left: 0;
}

.carousel-next {
  right: 0;
}

.carousel-dots {
  display: flex;
  gap: 8px;
  justify-content: center;
  margin-top: 1.25rem;
}

.carousel-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  border: none;
  background: var(--text-faint);
  cursor: pointer;
  transition: all var(--transition);
  padding: 0;
}

.carousel-dot:hover {
  background: var(--text-muted);
}

.carousel-dot.active {
  background: var(--text-primary);
  width: 24px;
  border-radius: 4px;
}

/* Counter label */
.carousel-counter {
  text-align: center;
  margin-top: 0.5rem;
  font-size: 0.78rem;
  color: var(--text-muted);
  font-weight: 500;
}

@media (max-width: 768px) {
  .carousel { padding: 0 2.25rem; }
  .carousel-prev { left: 0; }
  .carousel-next { right: 0; }
  .carousel-btn {
    width: 34px;
    height: 34px;
  }
}

/* ===== ANIMATIONS ===== */
.section-header,
.glass-card,
.demo-block {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.5s ease, transform 0.5s ease;
}
.section-header.visible,
.glass-card.visible,
.demo-block.visible {
  opacity: 1;
  transform: translateY(0);
}