:root {
  --bg-primary: #07090e;
  --bg-surface: #0f131d;
  --bg-card: #151a27;
  --bg-card-hover: #1c2333;
  --border-subtle: #232a3b;
  --border-strong: #384259;
  
  --text-main: #e2e8f0;
  --text-muted: #94a3b8;
  --text-dim: #64748b;
  
  --fast-color: #fbbf24;
  --fast-glow: rgba(251, 191, 36, 0.35);
  --fast-bg: rgba(251, 191, 36, 0.1);
  
  --slow-color: #f43f5e;
  --slow-glow: rgba(244, 63, 94, 0.35);
  --slow-bg: rgba(244, 63, 94, 0.1);
  
  --accent-cyan: #38bdf8;
  --accent-purple: #a855f7;
  
  --font-serif: "Newsreader", "Charter", "Georgia", serif;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", sans-serif;
  --font-mono: "JetBrains Mono", "SF Mono", "Menlo", monospace;
  
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 18px;
  --radius-full: 9999px;
  
  --max-w: 860px;
  --max-w-wide: 1100px;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  background-color: var(--bg-primary);
  color: var(--text-main);
  font-family: var(--font-sans);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

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

a {
  color: var(--accent-cyan);
  text-decoration: none;
  transition: color 0.15s ease;
}

a:hover {
  text-decoration: underline;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* Header */
.topbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.25rem 1.5rem;
  max-width: var(--max-w-wide);
  width: 100%;
  margin: 0 auto;
  border-bottom: 1px solid var(--border-subtle);
}

.brand {
  font-size: 0.95rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  color: var(--text-main);
}

.langsw {
  font-size: 0.875rem;
  color: var(--text-dim);
}

.langsw a {
  color: var(--text-muted);
  padding: 0.25rem 0.5rem;
  border-radius: var(--radius-sm);
}

.langsw a[aria-current="page"] {
  color: #fff;
  font-weight: 700;
  background: var(--border-subtle);
}

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

.container-wide {
  max-width: var(--max-w-wide);
  width: 100%;
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* Hero */
.hero {
  padding: 4rem 0 3rem;
  text-align: center;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.35rem 0.85rem;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-full);
  font-size: 0.825rem;
  font-family: var(--font-mono);
  color: var(--accent-cyan);
  margin-bottom: 1.5rem;
}

.hero h1 {
  font-family: var(--font-serif);
  font-size: clamp(2.25rem, 5vw, 3.5rem);
  font-weight: 700;
  line-height: 1.15;
  letter-spacing: -0.02em;
  color: #ffffff;
  margin-bottom: 1.25rem;
}

.hero-lead {
  font-size: clamp(1.1rem, 2.2vw, 1.25rem);
  color: var(--text-muted);
  max-width: 720px;
  margin: 0 auto 2.5rem;
  line-height: 1.6;
}

/* Metric Banner Grid */
.stat-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1.25rem;
  margin: 2rem 0 3rem;
}

.stat-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  position: relative;
  overflow: hidden;
  transition: transform 0.2s ease, border-color 0.2s ease;
}

.stat-card.fast {
  border-top: 3px solid var(--fast-color);
}

.stat-card.slow {
  border-top: 3px solid var(--slow-color);
}

.stat-card.diff {
  border-top: 3px solid var(--accent-cyan);
}

.stat-label {
  font-size: 0.85rem;
  font-family: var(--font-mono);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-dim);
  margin-bottom: 0.5rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.stat-val {
  font-family: var(--font-mono);
  font-size: 2.25rem;
  font-weight: 700;
  line-height: 1;
  color: #ffffff;
  margin-bottom: 0.35rem;
}

.stat-unit {
  font-size: 1rem;
  color: var(--text-muted);
  font-weight: 400;
}

.stat-desc {
  font-size: 0.875rem;
  color: var(--text-muted);
}

/* Section styling */
section {
  padding: 3rem 0;
  border-top: 1px solid var(--border-subtle);
}

.section-header {
  margin-bottom: 2rem;
}

.section-header h2 {
  font-family: var(--font-serif);
  font-size: 1.85rem;
  font-weight: 600;
  color: #ffffff;
  margin-bottom: 0.65rem;
}

.section-header p {
  color: var(--text-muted);
  font-size: 1.05rem;
  max-width: 680px;
}

/* Interactive Chronograph Tool */
.chronograph-box {
  background: var(--bg-surface);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-lg);
  padding: 2rem;
  margin-bottom: 2.5rem;
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.4);
}

.tool-controls {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 1.75rem;
  padding-bottom: 1.25rem;
  border-bottom: 1px solid var(--border-subtle);
}

.preset-group {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  align-items: center;
}

.preset-label {
  font-size: 0.85rem;
  color: var(--text-dim);
  font-family: var(--font-mono);
  margin-right: 0.25rem;
}

.btn-preset {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  color: var(--text-muted);
  padding: 0.5rem 0.85rem;
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  font-family: var(--font-sans);
  cursor: pointer;
  transition: all 0.15s ease;
}

.btn-preset:hover {
  background: var(--bg-card-hover);
  color: #ffffff;
  border-color: var(--border-strong);
}

.btn-preset.active {
  background: var(--accent-cyan);
  color: #07090e;
  font-weight: 600;
  border-color: var(--accent-cyan);
}

.action-group {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.btn-trigger {
  background: #ffffff;
  color: #07090e;
  border: none;
  padding: 0.65rem 1.35rem;
  border-radius: var(--radius-sm);
  font-size: 0.95rem;
  font-weight: 700;
  font-family: var(--font-sans);
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  box-shadow: 0 4px 12px rgba(255, 255, 255, 0.15);
  transition: transform 0.1s ease, background 0.15s ease;
}

.btn-trigger:hover {
  background: #f1f5f9;
  transform: translateY(-1px);
}

.btn-trigger:active {
  transform: translateY(0);
}

.btn-audio {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  color: var(--text-muted);
  padding: 0.65rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
}

.btn-audio.active {
  color: var(--accent-cyan);
  border-color: var(--accent-cyan);
}

/* Visualization Canvas & Track Area */
.sim-viewport {
  position: relative;
  background: #090c14;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
}

.tracks-container {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
  position: relative;
}

.track-lane {
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 1rem;
  position: relative;
}

.track-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.75rem;
  font-family: var(--font-mono);
  font-size: 0.85rem;
}

.track-name {
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.dot-indicator {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  display: inline-block;
}

.dot-fast {
  background: var(--fast-color);
  box-shadow: 0 0 8px var(--fast-color);
}

.dot-slow {
  background: var(--slow-color);
  box-shadow: 0 0 8px var(--slow-color);
}

.track-speed {
  color: var(--text-dim);
}

.track-rail {
  height: 18px;
  background: #121824;
  border-radius: 9px;
  position: relative;
  overflow: visible;
  border: 1px solid var(--border-subtle);
}

.pulse-node {
  position: absolute;
  top: 50%;
  left: 0;
  transform: translate(-50%, -50%);
  width: 22px;
  height: 22px;
  border-radius: 50%;
  z-index: 5;
  transition: left 0.05s linear;
}

.pulse-node.fast {
  background: var(--fast-color);
  box-shadow: 0 0 14px var(--fast-color), 0 0 24px var(--fast-glow);
}

.pulse-node.slow {
  background: var(--slow-color);
  box-shadow: 0 0 14px var(--slow-color), 0 0 24px var(--slow-glow);
}

.pulse-tail {
  position: absolute;
  top: 0;
  left: 0;
  height: 100%;
  border-radius: 9px;
  opacity: 0.4;
}

.pulse-tail.fast {
  background: linear-gradient(90deg, transparent, var(--fast-color));
}

.pulse-tail.slow {
  background: linear-gradient(90deg, transparent, var(--slow-color));
}

/* Chronograph HUD Readouts */
.hud-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
  margin-top: 1.5rem;
}

.hud-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 1rem;
}

.hud-title {
  font-size: 0.75rem;
  font-family: var(--font-mono);
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.25rem;
}

.hud-value {
  font-family: var(--font-mono);
  font-size: 1.5rem;
  font-weight: 700;
  color: #ffffff;
}

.hud-card.active-arrival-fast {
  border-color: var(--fast-color);
  background: var(--fast-bg);
}

.hud-card.active-arrival-slow {
  border-color: var(--slow-color);
  background: var(--slow-bg);
}

.hud-card.active-gap {
  border-color: var(--accent-cyan);
  background: rgba(56, 189, 248, 0.08);
}

/* Comparison Table */
.table-wrap {
  width: 100%;
  overflow-x: auto;
  margin: 2rem 0;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  background: var(--bg-surface);
}

table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.925rem;
}

th, td {
  padding: 1rem 1.25rem;
  border-bottom: 1px solid var(--border-subtle);
}

th {
  background: var(--bg-card);
  font-family: var(--font-mono);
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
}

tr:last-child td {
  border-bottom: none;
}

tbody tr:hover {
  background: rgba(255, 255, 255, 0.02);
}

.mono {
  font-family: var(--font-mono);
}

/* Prose and Scientific Content */
.prose {
  font-size: 1.075rem;
  line-height: 1.75;
  color: #cbd5e1;
}

.prose p {
  margin-bottom: 1.5rem;
}

.prose strong {
  color: #ffffff;
}

.prose h3 {
  font-family: var(--font-serif);
  font-size: 1.45rem;
  font-weight: 600;
  color: #ffffff;
  margin: 2.25rem 0 1rem;
}

.callout {
  background: var(--bg-surface);
  border-left: 4px solid var(--accent-cyan);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  padding: 1.25rem 1.5rem;
  margin: 2rem 0;
}

.callout p {
  margin-bottom: 0;
  font-size: 1rem;
  color: var(--text-muted);
}

.callout strong {
  color: #ffffff;
}

/* Squid Axon Calculator */
.calc-box {
  background: var(--bg-surface);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-md);
  padding: 2rem;
  margin: 2rem 0;
}

.calc-slider-wrap {
  margin: 1.5rem 0;
}

.slider-label-row {
  display: flex;
  justify-content: space-between;
  font-family: var(--font-mono);
  font-size: 0.9rem;
  margin-bottom: 0.5rem;
}

input[type="range"] {
  width: 100%;
  height: 6px;
  background: var(--border-strong);
  border-radius: 3px;
  outline: none;
  -webkit-appearance: none;
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--accent-cyan);
  cursor: pointer;
  box-shadow: 0 0 10px rgba(56, 189, 248, 0.5);
}

.calc-results-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1.25rem;
  margin-top: 1.5rem;
}

.calc-res-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 1.25rem;
}

.calc-res-card.highlight {
  border-color: var(--slow-color);
  background: var(--slow-bg);
}

/* Method Note Section */
.method-note {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 2rem;
  margin-top: 3rem;
  font-size: 0.925rem;
  color: var(--text-muted);
}

.method-note h3 {
  font-family: var(--font-serif);
  font-size: 1.25rem;
  color: #ffffff;
  margin-bottom: 1rem;
}

.method-note ul {
  padding-left: 1.25rem;
  margin-bottom: 1rem;
}

.method-note li {
  margin-bottom: 0.5rem;
}

/* Footer */
footer {
  margin-top: auto;
  border-top: 1px solid var(--border-subtle);
  padding: 2.5rem 0;
  text-align: center;
  font-size: 0.875rem;
  color: var(--text-dim);
}

.back-to-top {
  display: inline-block;
  margin-bottom: 1rem;
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* 404 Page */
.page-404 {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
}

.error-card {
  text-align: center;
  padding: 3rem 2rem;
  background: var(--bg-surface);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-lg);
  max-width: 480px;
  margin: 0 auto;
}

.badge {
  display: inline-block;
  padding: 0.25rem 0.75rem;
  border-radius: var(--radius-full);
  background: var(--slow-bg);
  color: var(--slow-color);
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 0.9rem;
  margin-bottom: 1rem;
}

.error-card h1 {
  font-size: 1.75rem;
  margin-bottom: 0.75rem;
  color: #fff;
}

.error-card p {
  color: var(--text-muted);
  margin-bottom: 1.5rem;
}

.btn-primary {
  display: inline-block;
  background: var(--accent-cyan);
  color: #07090e;
  font-weight: 600;
  padding: 0.65rem 1.25rem;
  border-radius: var(--radius-sm);
  text-decoration: none;
}

/* Responsiveness */
@media (max-width: 640px) {
  .hero {
    padding: 2.5rem 0 2rem;
  }
  .chronograph-box {
    padding: 1.25rem;
  }
  .stat-grid {
    grid-template-columns: 1fr;
  }
  .tool-controls {
    flex-direction: column;
    align-items: stretch;
  }
  .preset-group {
    justify-content: flex-start;
  }
  .action-group {
    justify-content: space-between;
  }
  .btn-trigger {
    flex: 1;
    justify-content: center;
  }
}