:root {
  --bg: #0a0a0f;
  --bg-card: #12121a;
  --bg-hover: #1a1a25;
  --accent: #00ffc8;
  --accent-dim: #00aa88;
  --secondary: #ff6b35;
  --tertiary: #8b5cf6;
  --text: #e8e8f0;
  --text-dim: #888899;
  --border: #2a2a3a;
  --empty: #1a1a25;
  --filled: #00aa88;
  --filled-hover: #00ffc8;
}

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

body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: 'Inter', -apple-system, system-ui, sans-serif;
  line-height: 1.6;
}

#root {
  min-height: 100vh;
}

/* Navigation */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(10, 10, 15, 0.9);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
  padding: 0.75rem 1.5rem;
}

.nav-inner {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  gap: 0.5rem;
  overflow-x: auto;
  justify-content: center;
  flex-wrap: wrap;
  -webkit-overflow-scrolling: touch;
}

.nav-link {
  padding: 0.5rem 1rem;
  border-radius: 999px;
  border: 1px solid transparent;
  color: var(--text-dim);
  text-decoration: none;
  white-space: nowrap;
  font-size: 0.8rem;
  transition: color 0.2s ease, border-color 0.2s ease, background 0.2s ease;
}

.nav-link:hover,
.nav-link:focus-visible {
  color: var(--accent);
  border-color: var(--border);
}

.nav-link--active {
  background: rgba(0, 255, 200, 0.08);
  color: var(--accent);
  border-color: var(--accent);
}

/* Hero */
.hero {
  padding: 6.25rem 1.5rem;
  text-align: center;
  background: linear-gradient(180deg, var(--bg) 0%, #0f1018 100%);
  border-bottom: 1px solid var(--border);
}

.hero-eyebrow {
  font-size: 0.75rem;
  letter-spacing: 3px;
  color: var(--accent);
  margin-bottom: 1.5rem;
  text-transform: uppercase;
}

.hero-title {
  font-size: clamp(3rem, 10vw, 5rem);
  font-weight: 800;
  margin: 0 0 1.5rem;
  background: linear-gradient(135deg, var(--accent) 0%, var(--tertiary) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  font-family: 'Space Grotesk', system-ui, sans-serif;
}

.hero-subtitle {
  font-size: 1.25rem;
  color: var(--text-dim);
  max-width: 600px;
  margin: 0 auto 2.5rem;
  line-height: 1.6;
}

.hero-demo {
  display: inline-flex;
  gap: 4px;
  font-size: 2rem;
  font-family: 'Space Mono', monospace;
  color: var(--accent);
}

/* At a glance */
.at-a-glance {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
  max-width: 600px;
  margin: 2rem auto 0;
}

.at-a-glance-item {
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border);
  border-radius: 0.5rem;
  padding: 1rem;
  text-align: center;
}

.at-a-glance-item strong {
  display: block;
  color: var(--accent);
  font-size: 0.9rem;
  margin-bottom: 0.25rem;
}

.at-a-glance-item span {
  font-size: 0.8rem;
  color: var(--text-dim);
}

/* Sections */
.section {
  padding: 5rem 1.5rem;
  border-bottom: 1px solid var(--border);
  max-width: 900px;
  margin: 0 auto;
}

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

.section-title {
  font-size: 2.25rem;
  font-weight: 700;
  margin: 0 0 0.75rem;
  font-family: 'Space Grotesk', system-ui, sans-serif;
}

.section-title--accent { color: var(--accent); }
.section-title--secondary { color: var(--secondary); }
.section-title--tertiary { color: var(--tertiary); }

.section-subtitle {
  font-size: 1.125rem;
  color: var(--text-dim);
  margin: 0;
  max-width: 600px;
  margin-inline: auto;
}

/* Cards */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  padding: 1.5rem;
}

.card-grid {
  display: grid;
  gap: 1.5rem;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

.intro-card {
  transition: all 0.3s ease;
}

.intro-card-icon {
  font-size: 2.25rem;
  margin-bottom: 1rem;
}

.intro-card-title {
  color: var(--accent);
  margin: 0 0 0.75rem;
  font-size: 1.125rem;
}

.intro-card-text {
  color: var(--text-dim);
  margin: 0;
  line-height: 1.6;
  font-size: 0.875rem;
}

/* Buttons */
.btn {
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 0.625rem 1.25rem;
  border-radius: 0.375rem;
  cursor: pointer;
  font-size: 0.875rem;
  font-weight: 500;
  font-family: inherit;
  transition: all 0.2s ease;
}

.btn:hover,
.btn:focus-visible {
  background: var(--bg-hover);
  border-color: var(--accent);
  color: var(--accent);
}

.btn--active {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--bg);
}

.btn-group {
  display: flex;
  gap: 0.75rem;
  justify-content: center;
  flex-wrap: wrap;
}

/* Tile Grid */
.tile-grid-container {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  align-items: center;
}

.tile-grid {
  display: grid;
  gap: 2px;
  background: var(--border);
  padding: 2px;
  border-radius: 0.5rem;
  user-select: none;
}

.tile-grid--8x10 { grid-template-columns: repeat(10, 1fr); }
.tile-grid--6x6 { grid-template-columns: repeat(6, 1fr); }

.tile-grid-cell {
  width: 40px;
  height: 40px;
  background: var(--empty);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all 0.15s ease;
  font-family: 'Space Mono', monospace;
  font-weight: 700;
  color: var(--text-dim);
  border-radius: 2px;
}

.tile-grid-cell[data-filled="true"] {
  background: var(--filled);
  color: var(--text);
}

.tile-grid-cell:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.tile-grid-cell--4bit {
  font-size: 1.5rem;
}

.tile-grid-cell--8bit {
  font-size: 0.75rem;
}

/* Bitmask Calculator */
.bitmask-calculator {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
  align-items: center;
}

.mode-selector {
  display: flex;
  gap: 0.75rem;
}

.neighbor-grid {
  display: grid;
  grid-template-columns: repeat(3, 80px);
  gap: 4px;
}

.neighbor-cell {
  width: 80px;
  height: 80px;
  border: 2px solid var(--border);
  border-radius: 0.5rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all 0.2s ease;
  position: relative;
}

.neighbor-cell--center {
  background: var(--tertiary);
  border-color: var(--tertiary);
  cursor: default;
}

.neighbor-cell--active {
  background: var(--filled);
  border-color: var(--accent);
}

.neighbor-cell--disabled {
  opacity: 0.3;
  cursor: not-allowed;
}

.neighbor-cell--dimmed {
  opacity: 0.3;
}

.neighbor-cell:not(.neighbor-cell--center):not(.neighbor-cell--disabled):focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.neighbor-label {
  font-size: 0.875rem;
  font-weight: 700;
  color: var(--text);
}

.bit-info {
  font-size: 0.7rem;
  color: var(--text-dim);
  position: absolute;
  bottom: 4px;
}

.mask-result {
  background: var(--bg-card);
  padding: 1.5rem 2rem;
  border-radius: 0.75rem;
  border: 1px solid var(--border);
  text-align: center;
}

.mask-binary {
  font-size: 0.875rem;
  color: var(--text-dim);
  margin-bottom: 0.5rem;
}

.mask-binary-code {
  font-family: 'Space Mono', monospace;
  color: var(--accent);
}

.mask-value {
  font-size: 3rem;
  font-weight: 700;
  color: var(--accent);
  font-family: 'Space Mono', monospace;
  margin: 0;
}

.mask-description {
  font-size: 0.875rem;
  color: var(--text-dim);
  margin-top: 0.5rem;
}

/* Binary Visualizer */
.binary-visualizer {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
  align-items: center;
}

.slider-control {
  display: flex;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
  justify-content: center;
}

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

.slider {
  width: 200px;
  accent-color: var(--accent);
}

.slider-value {
  font-family: 'Space Mono', monospace;
  font-size: 1.5rem;
  color: var(--accent);
  min-width: 50px;
  text-align: center;
}

.binary-bits {
  display: flex;
  gap: 0.5rem;
}

.binary-bit {
  width: 60px;
  height: 80px;
  border: 2px solid var(--border);
  border-radius: 0.5rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all 0.2s ease;
}

.binary-bit--active {
  background: var(--filled);
  border-color: var(--accent);
}

.binary-bit:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.bit-value {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text);
}

.bit-power {
  font-size: 0.6rem;
  color: var(--text-dim);
}

.bit-decimal {
  font-size: 0.6rem;
  color: var(--accent);
}

.binary-equation {
  font-family: 'Space Mono', monospace;
  font-size: 0.875rem;
  color: var(--text-dim);
  background: var(--bg-card);
  padding: 1rem 1.5rem;
  border-radius: 0.5rem;
  border: 1px solid var(--border);
  max-width: 100%;
  overflow-wrap: break-word;
}

.equation-value {
  color: var(--accent);
  font-weight: 700;
}

/* Quarter Tile Demo */
.quarter-demo {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
  align-items: center;
}

.quarter-preview {
  display: flex;
  gap: 3rem;
  align-items: center;
  flex-wrap: wrap;
  justify-content: center;
}

.quarter-grid {
  display: grid;
  grid-template-columns: repeat(2, 60px);
  gap: 4px;
  background: var(--border);
  padding: 4px;
  border-radius: 0.5rem;
}

.quarter-tile {
  width: 60px;
  height: 60px;
  border-radius: 4px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--bg);
}

.quarter-legend {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.legend-item {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.legend-color {
  width: 20px;
  height: 20px;
  border-radius: 4px;
}

.legend-label {
  font-size: 0.75rem;
  color: var(--text-dim);
}

/* Reference Grid */
.tile-reference {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.5rem;
  max-width: 400px;
  margin: 0 auto;
}

.reference-tile {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 0.5rem;
  padding: 0.75rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.25rem;
}

.reference-char {
  font-size: 1.75rem;
  font-family: 'Space Mono', monospace;
  color: var(--accent);
}

.reference-label {
  font-size: 0.75rem;
  color: var(--text-dim);
}

/* Comparison Demo */
.comparison-demo {
  display: flex;
  gap: 3rem;
  justify-content: center;
  flex-wrap: wrap;
}

.comparison-side {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.75rem;
}

.comparison-title {
  margin: 0;
  font-size: 1.125rem;
}

.comparison-title--before { color: var(--secondary); }
.comparison-title--after { color: var(--accent); }

.comparison-grid {
  display: grid;
  grid-template-columns: repeat(6, 40px);
  gap: 2px;
  background: var(--border);
  padding: 2px;
  border-radius: 0.5rem;
}

.comparison-cell {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
  color: var(--text);
}

.comparison-cell--filled {
  background: var(--filled);
}

.comparison-cell--empty {
  background: var(--empty);
}

.comparison-cell--char {
  font-size: 1.5rem;
  font-family: 'Space Mono', monospace;
}

.comparison-caption {
  font-size: 0.75rem;
  color: var(--text-dim);
}

/* Code Blocks */
.code-block {
  background: #0d0d12;
  border: 1px solid var(--border);
  border-radius: 0.5rem;
  padding: 1.25rem;
  overflow: auto;
  font-size: 0.8rem;
  line-height: 1.6;
  font-family: 'Space Mono', monospace;
  color: var(--text);
  margin: 1.5rem 0;
}

.code-block code {
  font-family: inherit;
}

/* Key Concepts */
.key-concepts {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  padding: 1.5rem;
  margin-top: 2rem;
}

.key-concepts h4 {
  color: var(--accent);
  margin: 0 0 0.75rem;
}

.key-concepts ul {
  color: var(--text-dim);
  margin: 0;
  padding-left: 1.25rem;
  line-height: 2;
}

.key-concepts strong {
  color: var(--text);
}

/* Integration Example */
.integration-example {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  padding: 1.5rem;
  margin: 2rem 0;
}

.integration-example h4 {
  color: var(--secondary);
  margin: 0 0 1rem;
}

.integration-steps {
  list-style: none;
  padding: 0;
  margin: 0;
}

.integration-steps li {
  padding: 0.5rem 0;
  border-bottom: 1px solid rgba(255, 255, 255, 0.05);
  color: var(--text-dim);
}

.integration-steps li:last-child {
  border-bottom: none;
}

.integration-steps strong {
  color: var(--accent);
}

/* Implementation sections */
.implementation-section {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.implementation-step h4 {
  color: var(--accent);
  margin-bottom: 0.75rem;
}

/* Footer */
.footer {
  padding: 3.75rem 1.5rem;
  text-align: center;
  border-top: 1px solid var(--border);
}

.footer-icon {
  font-family: 'Space Mono', monospace;
  font-size: 1.5rem;
  color: var(--accent);
  margin-bottom: 1.5rem;
}

.footer-title {
  color: var(--text);
  margin: 0 0 1rem;
}

.footer-links {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 2rem;
}

.footer-link {
  color: var(--text-dim);
  font-size: 0.875rem;
  padding: 0.5rem 1rem;
  background: var(--bg-card);
  border-radius: 999px;
  border: 1px solid var(--border);
  text-decoration: none;
}

.footer-credit {
  color: var(--text-dim);
  font-size: 0.8rem;
}

/* Mobile responsiveness */
@media (max-width: 768px) {
  .section {
    padding: 3rem 1rem;
  }
  
  .hero {
    padding: 4rem 1rem;
  }
  
  .comparison-demo {
    gap: 2rem;
  }
  
  .quarter-preview {
    gap: 2rem;
  }
  
  .binary-bits {
    flex-wrap: wrap;
    justify-content: center;
  }
  
  .tile-grid-cell {
    width: 35px;
    height: 35px;
  }
  
  .neighbor-cell {
    width: 70px;
    height: 70px;
  }
  
  .at-a-glance {
    grid-template-columns: 1fr;
    gap: 0.75rem;
  }
}

@media (max-width: 480px) {
  .hero-title {
    font-size: 2.5rem;
  }
  
  .section-title {
    font-size: 1.75rem;
  }
  
  .tile-grid-cell {
    width: 32px;
    height: 32px;
    font-size: 0.875rem;
  }
  
  .neighbor-cell {
    width: 60px;
    height: 60px;
  }
  
  .binary-bit {
    width: 50px;
    height: 70px;
  }
}

/* Focus management */
.skip-link {
  position: absolute;
  top: -40px;
  left: 6px;
  background: var(--accent);
  color: var(--bg);
  padding: 0.5rem 1rem;
  border-radius: 0.25rem;
  text-decoration: none;
  z-index: 1000;
  font-weight: 600;
}

.skip-link:focus {
  top: 6px;
}

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