/* Sigma-Model: Academic Research & Reproducibility Portal Stylesheet */
:root {
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-serif: "Charter", "Bitstream Charter", "Sitka Text", "Cambria", Georgia, serif;
  --font-mono: "JetBrains Mono", "Fira Code", Menlo, Monaco, Consolas, monospace;

  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-card: #ffffff;
  --bg-card-hover: #f1f5f9;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #64748b;
  --border-color: #e2e8f0;
  --border-subtle: #cbd5e1;

  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --primary-light: #eff6ff;
  --secondary: #4f46e5;
  --accent: #0284c7;
  --success: #16a34a;
  --success-bg: #f0fdf4;
  --warning: #d97706;
  --warning-bg: #fffbeb;
  --danger: #dc2626;
  --danger-bg: #fef2f2;
  --purple: #7c3aed;
  --purple-bg: #faf5ff;

  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-full: 9999px;

  --max-w: 1200px;
}

[data-theme="dark"] {
  --bg-primary: #090d16;
  --bg-secondary: #0f172a;
  --bg-card: #131d33;
  --bg-card-hover: #1e293b;
  --text-primary: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;
  --border-color: #1e293b;
  --border-subtle: #334155;

  --primary: #3b82f6;
  --primary-hover: #60a5fa;
  --primary-light: rgba(59, 130, 246, 0.15);
  --success-bg: rgba(22, 163, 74, 0.15);
  --warning-bg: rgba(217, 119, 6, 0.15);
  --danger-bg: rgba(220, 38, 38, 0.15);
  --purple-bg: rgba(124, 58, 237, 0.15);

  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.3);
  --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.3);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.4);
}

*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  font-family: var(--font-sans);
  color: var(--text-primary);
  background-color: var(--bg-secondary);
  line-height: 1.6;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

a {
  color: var(--primary);
  text-decoration: none;
  transition: color 0.15s ease;
}
a:hover {
  color: var(--primary-hover);
  text-decoration: underline;
}

/* Header & Nav */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background-color: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border-color);
  transition: background-color 0.3s ease, border-color 0.3s ease;
}
[data-theme="dark"] .site-header {
  background-color: rgba(9, 13, 22, 0.92);
}

.nav-container {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0.85rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-weight: 700;
  font-size: 1.15rem;
  color: var(--text-primary);
}
.brand .greek-sigma {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  background: linear-gradient(135deg, var(--primary), var(--purple));
  color: white;
  border-radius: var(--radius-sm);
  font-family: var(--font-serif);
  font-size: 1.25rem;
  font-weight: 700;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  list-style: none;
}
.nav-links a {
  font-size: 0.92rem;
  font-weight: 500;
  color: var(--text-secondary);
}
.nav-links a:hover, .nav-links a.active {
  color: var(--primary);
  text-decoration: none;
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.theme-toggle {
  background: transparent;
  border: 1px solid var(--border-color);
  padding: 0.4rem 0.6rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  color: var(--text-secondary);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s;
}
.theme-toggle:hover {
  background-color: var(--bg-card-hover);
}

/* Hero Section */
.hero {
  background: radial-gradient(circle at 50% 10%, rgba(37, 99, 235, 0.08), transparent 70%), var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  padding: 4rem 1.5rem 3.5rem;
  text-align: center;
}
.hero-content {
  max-width: 900px;
  margin: 0 auto;
}
.hero-badge-group {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
}
.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.8rem;
  font-weight: 600;
  padding: 0.25rem 0.65rem;
  border-radius: var(--radius-full);
  border: 1px solid transparent;
}
.badge-blue {
  background-color: var(--primary-light);
  color: var(--primary);
  border-color: rgba(37, 99, 235, 0.3);
}
.badge-green {
  background-color: var(--success-bg);
  color: var(--success);
  border-color: rgba(22, 163, 74, 0.3);
}
.badge-purple {
  background-color: var(--purple-bg);
  color: var(--purple);
  border-color: rgba(124, 58, 237, 0.3);
}

.hero-title {
  font-family: var(--font-serif);
  font-size: 2.65rem;
  line-height: 1.22;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 1.25rem;
  letter-spacing: -0.02em;
}
.hero-subtitle {
  font-size: 1.18rem;
  color: var(--text-secondary);
  margin-bottom: 1.5rem;
  line-height: 1.55;
  font-weight: 400;
}
.hero-authors {
  font-size: 0.95rem;
  color: var(--text-muted);
  margin-bottom: 2rem;
}
.hero-authors strong {
  color: var(--text-primary);
}

.hero-buttons {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 0.85rem;
  margin-bottom: 2rem;
}
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.95rem;
  font-weight: 600;
  padding: 0.65rem 1.25rem;
  border-radius: var(--radius-md);
  border: 1px solid transparent;
  cursor: pointer;
  transition: all 0.2s ease;
  text-decoration: none;
}
.btn-primary {
  background-color: var(--primary);
  color: white;
  box-shadow: 0 2px 4px rgba(37, 99, 235, 0.25);
}
.btn-primary:hover {
  background-color: var(--primary-hover);
  color: white;
  text-decoration: none;
  box-shadow: 0 4px 8px rgba(37, 99, 235, 0.35);
}
.btn-outline {
  background-color: var(--bg-card);
  color: var(--text-primary);
  border-color: var(--border-color);
  box-shadow: var(--shadow-sm);
}
.btn-outline:hover {
  background-color: var(--bg-card-hover);
  border-color: var(--border-subtle);
  color: var(--text-primary);
  text-decoration: none;
}

/* Main Container */
.container {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 2.5rem 1.5rem;
  width: 100%;
}

.section {
  margin-bottom: 3.5rem;
}
.section-header {
  margin-bottom: 1.75rem;
}
.section-tag {
  display: inline-block;
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--primary);
  margin-bottom: 0.35rem;
}
.section-title {
  font-family: var(--font-serif);
  font-size: 1.95rem;
  color: var(--text-primary);
  margin-bottom: 0.5rem;
}
.section-desc {
  font-size: 1.02rem;
  color: var(--text-secondary);
  max-width: 820px;
}

/* Card & Grid Styles */
.grid-2 {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 1.5rem;
}
.grid-3 {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
}
.grid-4 {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1rem;
}

.card {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  box-shadow: var(--shadow-sm);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}
.card:hover {
  box-shadow: var(--shadow);
}
.card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1rem;
}
.card-title {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text-primary);
}
.card-body {
  color: var(--text-secondary);
  font-size: 0.95rem;
}

/* Interactive Bifurcation Explorer */
.interactive-panel {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  box-shadow: var(--shadow);
}
.explorer-layout {
  display: grid;
  grid-template-columns: 1fr 340px;
  gap: 2rem;
  align-items: start;
}
@media (max-width: 900px) {
  .explorer-layout {
    grid-template-columns: 1fr;
  }
}

.canvas-container {
  position: relative;
  width: 100%;
  aspect-ratio: 16 / 10;
  background-color: var(--bg-secondary);
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
  overflow: hidden;
}
.canvas-container canvas {
  width: 100%;
  height: 100%;
  display: block;
}

.controls-panel {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}
.control-group {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}
.control-label {
  display: flex;
  justify-content: space-between;
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--text-primary);
}
.control-slider {
  width: 100%;
  height: 6px;
  border-radius: 3px;
  background: var(--border-subtle);
  outline: none;
  cursor: pointer;
}
.regime-indicator {
  padding: 0.9rem;
  border-radius: var(--radius-md);
  font-size: 0.9rem;
  line-height: 1.45;
  border: 1px solid var(--border-color);
}
.regime-subcritical {
  background-color: var(--danger-bg);
  border-color: rgba(220, 38, 38, 0.3);
  color: var(--text-primary);
}
.regime-supercritical {
  background-color: var(--success-bg);
  border-color: rgba(22, 163, 74, 0.3);
  color: var(--text-primary);
}

.stat-callout {
  display: flex;
  flex-direction: column;
  padding: 0.75rem 1rem;
  background-color: var(--bg-secondary);
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
}
.stat-val {
  font-family: var(--font-mono);
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--text-primary);
}
.stat-lbl {
  font-size: 0.75rem;
  text-transform: uppercase;
  color: var(--text-muted);
  font-weight: 600;
}

/* Tables */
.table-wrapper {
  overflow-x: auto;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  background-color: var(--bg-card);
  box-shadow: var(--shadow-sm);
}
table.academic-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.92rem;
}
table.academic-table th {
  background-color: var(--bg-secondary);
  padding: 0.85rem 1rem;
  font-weight: 600;
  color: var(--text-primary);
  border-bottom: 2px solid var(--border-color);
  white-space: nowrap;
}
table.academic-table td {
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--border-color);
  color: var(--text-secondary);
}
table.academic-table tbody tr:hover {
  background-color: var(--bg-card-hover);
}
table.academic-table tr:last-child td {
  border-bottom: none;
}
.mono-cell {
  font-family: var(--font-mono);
  font-size: 0.86rem;
}

/* Callouts / Alerts */
.callout {
  padding: 1.25rem 1.5rem;
  border-radius: var(--radius-md);
  margin-bottom: 1.5rem;
  border-left: 4px solid var(--primary);
  background-color: var(--bg-secondary);
}
.callout-info {
  border-left-color: var(--primary);
  background-color: var(--primary-light);
}
.callout-success {
  border-left-color: var(--success);
  background-color: var(--success-bg);
}
.callout-warning {
  border-left-color: var(--warning);
  background-color: var(--warning-bg);
}
.callout-title {
  font-weight: 700;
  font-size: 0.98rem;
  color: var(--text-primary);
  margin-bottom: 0.35rem;
}

/* Code & BibTeX */
.code-block {
  position: relative;
  background-color: #0d1117;
  color: #c9d1d9;
  border-radius: var(--radius-md);
  padding: 1.25rem;
  font-family: var(--font-mono);
  font-size: 0.86rem;
  line-height: 1.5;
  overflow-x: auto;
  border: 1px solid #30363d;
}
.code-block pre {
  margin: 0;
}
.copy-btn {
  position: absolute;
  top: 0.75rem;
  right: 0.75rem;
  padding: 0.35rem 0.75rem;
  font-size: 0.75rem;
  font-weight: 600;
  background-color: #21262d;
  color: #c9d1d9;
  border: 1px solid #30363d;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all 0.2s;
}
.copy-btn:hover {
  background-color: #30363d;
}

/* Figure gallery */
.figure-card {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}
.figure-img-wrap {
  width: 100%;
  background-color: #ffffff;
  border-bottom: 1px solid var(--border-color);
  padding: 1rem;
  display: flex;
  justify-content: center;
  align-items: center;
}
.figure-img-wrap img {
  max-width: 100%;
  height: auto;
  object-fit: contain;
  border-radius: 4px;
}
.figure-caption {
  padding: 1.2rem;
  font-size: 0.88rem;
  color: var(--text-secondary);
  line-height: 1.5;
}
.figure-caption strong {
  color: var(--text-primary);
}

/* Footer */
.site-footer {
  margin-top: auto;
  background-color: var(--bg-card);
  border-top: 1px solid var(--border-color);
  padding: 3rem 1.5rem;
  font-size: 0.9rem;
  color: var(--text-muted);
}
.footer-container {
  max-width: var(--max-w);
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 2rem;
}
.footer-left {
  max-width: 450px;
}
.footer-left p {
  margin-top: 0.5rem;
  line-height: 1.5;
}
.footer-links {
  display: flex;
  gap: 3rem;
}
.footer-col h4 {
  color: var(--text-primary);
  font-size: 0.92rem;
  margin-bottom: 0.75rem;
}
.footer-col ul {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.45rem;
}
.footer-col a {
  color: var(--text-muted);
}
.footer-col a:hover {
  color: var(--primary);
}