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

  :root {
    --bg: #212529;
    --bg-light: #2b3035;
    --bg-card: #2e3338;
    --bg-hover: #363b41;
    --accent: #00d4aa;
    --accent-dim: #00d4aa33;
    --accent-glow: #00d4aa66;
    --text: #e8eaed;
    --text-dim: #9aa0a6;
    --text-muted: #6c757d;
    --danger: #ff6b6b;
    --warning: #ffd43b;
    --border: #3a3f44;
    --radius: 12px;
    --radius-sm: 8px;
    --shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
    --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
  }

  body {
    font-family: 'Outfit', sans-serif;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    overflow-x: hidden;
  }

  .header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 24px;
    border-bottom: 1px solid var(--border);
    background: var(--bg);
    position: sticky;
    top: 0;
    z-index: 100;
    backdrop-filter: blur(12px);
  }

  .header-brand {
    flex-shrink: 0;
  }

  .header-brand img {
    display: block;
    height: 40px;
    width: auto;
  }

  .header-title {
    position: absolute;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.1rem;
    font-weight: 600;
    letter-spacing: -0.02em;
    white-space: nowrap;
  }

  .header-title span {
    color: var(--accent);
  }

  @media (max-width: 768px) {
    .header-title {
      display: none;
    }

    .header-brand img {
      height: 32px;
    }
  }

  /* @media (max-width: 768px) {
    .header-title {
      position: static;
      transform: none;
      font-size: 0.9rem;
    }

    .header-brand img {
      height: 32px;
    }
  } */

  .header-brand svg {
    width: 32px;
    height: 32px;
  }

  .header-brand h1 {
    font-size: 1.15rem;
    font-weight: 600;
    letter-spacing: -0.02em;
  }

  .header-brand span {
    color: var(--accent);
  }

  .header-badge {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.7rem;
    padding: 4px 10px;
    background: var(--accent-dim);
    color: var(--accent);
    border-radius: 20px;
    border: 1px solid var(--accent-glow);
  }

  /* Main Layout */
  .app-layout {
    display: grid;
    grid-template-columns: 280px 1fr 300px;
    height: calc(100vh - 65px);
  }

  @media (max-width: 1100px) {
    .app-layout {
      grid-template-columns: 1fr;
      height: auto;
    }
  }

  /* Sidebar */
  .sidebar {
    border-right: 1px solid var(--border);
    padding: 20px;
    overflow-y: auto;
    background: var(--bg);
  }

  @media (max-width: 1100px) {
    .sidebar {
      border-right: none;
      border-bottom: 1px solid var(--border);
      display: flex;
      flex-wrap: wrap;
      gap: 12px;
      padding: 16px;
    }

    .sidebar .section {
      flex: 1;
      min-width: 220px;
    }
  }

  .section {
    margin-bottom: 24px;
  }

  .section-title {
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--text-muted);
    margin-bottom: 12px;
    display: flex;
    align-items: center;
    gap: 6px;
  }

  .section-title::before {
    content: '';
    width: 3px;
    height: 12px;
    background: var(--accent);
    border-radius: 2px;
  }

  /* Controls */
  .control-group {
    margin-bottom: 14px;
  }

  .control-label {
    font-size: 0.8rem;
    color: var(--text-dim);
    margin-bottom: 6px;
    display: block;
  }

  .slider-row {
    display: flex;
    align-items: center;
    gap: 10px;
  }

  .slider-row input[type="range"] {
    flex: 1;
    -webkit-appearance: none;
    appearance: none;
    height: 4px;
    background: var(--border);
    border-radius: 2px;
    outline: none;
  }

  .slider-row input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 16px;
    height: 16px;
    border-radius: 50%;
    background: var(--accent);
    cursor: pointer;
    box-shadow: 0 0 8px var(--accent-glow);
    transition: var(--transition);
  }

  .slider-row input[type="range"]::-webkit-slider-thumb:hover {
    transform: scale(1.2);
    box-shadow: 0 0 16px var(--accent-glow);
  }

  .slider-value {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.8rem;
    min-width: 24px;
    text-align: right;
    color: var(--accent);
    font-weight: 500;
  }

  /* Buttons */
  .btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 10px 16px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
    background: var(--bg-card);
    color: var(--text);
    font-family: 'Outfit', sans-serif;
    font-size: 0.85rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    width: 100%;
  }

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

  .btn:active {
    transform: scale(0.97);
  }

  .btn-accent {
    background: var(--accent);
    color: var(--bg);
    border-color: var(--accent);
    font-weight: 600;
  }

  .btn-accent:hover {
    background: #00eabb;
    color: var(--bg);
    box-shadow: 0 0 20px var(--accent-glow);
  }

  .btn-danger {
    border-color: var(--danger);
    color: var(--danger);
  }

  .btn-danger:hover {
    background: #ff6b6b22;
  }

  .btn-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 8px;
  }

  .btn-sm {
    padding: 8px 12px;
    font-size: 0.78rem;
  }

  /* Toggle */
  .toggle-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 8px 0;
  }

  .toggle-label {
    font-size: 0.82rem;
    color: var(--text-dim);
  }

  .toggle {
    width: 40px;
    height: 22px;
    background: var(--border);
    border-radius: 11px;
    cursor: pointer;
    position: relative;
    transition: var(--transition);
    border: none;
    outline: none;
  }

  .toggle.active {
    background: var(--accent);
  }

  .toggle::after {
    content: '';
    width: 16px;
    height: 16px;
    background: white;
    border-radius: 50%;
    position: absolute;
    top: 3px;
    left: 3px;
    transition: var(--transition);
  }

  .toggle.active::after {
    left: 21px;
  }

  /* Presets */
  .preset-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 6px;
  }

  .preset-btn {
    padding: 8px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
    background: var(--bg-card);
    color: var(--text-dim);
    font-family: 'Outfit', sans-serif;
    font-size: 0.72rem;
    cursor: pointer;
    transition: var(--transition);
    text-align: center;
  }

  .preset-btn:hover {
    border-color: var(--accent);
    color: var(--accent);
    background: var(--accent-dim);
  }

  .preset-btn.active {
    border-color: var(--accent);
    color: var(--accent);
    background: var(--accent-dim);
    font-weight: 600;
  }

  /* 3D Viewport */
  .viewport {
    position: relative;
    overflow: hidden;
    background: var(--bg);
  }

  #canvas3d {
    width: 100%;
    height: 100%;
    display: block;
  }

  .viewport-overlay {
    position: absolute;
    bottom: 16px;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    gap: 8px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 6px 10px;
    backdrop-filter: blur(12px);
  }

  .viewport-btn {
    width: 36px;
    height: 36px;
    border-radius: var(--radius-sm);
    border: none;
    background: transparent;
    color: var(--text-dim);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
    font-size: 1.1rem;
  }

  .viewport-btn:hover {
    background: var(--bg-hover);
    color: var(--accent);
  }

  .viewport-hint {
    position: absolute;
    top: 16px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 0.75rem;
    color: var(--text-muted);
    background: var(--bg-card);
    border: 1px solid var(--border);
    padding: 6px 14px;
    border-radius: 20px;
    opacity: 0.8;
    pointer-events: none;
  }

  /* Info Panel (right sidebar) */
  .info-panel {
    border-left: 1px solid var(--border);
    padding: 20px;
    overflow-y: auto;
    background: var(--bg);
  }

  @media (max-width: 1100px) {
    .info-panel {
      border-left: none;
      border-top: 1px solid var(--border);
      padding: 16px;
    }
  }

  .info-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 16px;
    margin-bottom: 12px;
  }

  .info-card-title {
    font-size: 0.72rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-muted);
    margin-bottom: 10px;
  }

  .info-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 6px 0;
    border-bottom: 1px solid var(--border);
  }

  .info-row:last-child {
    border-bottom: none;
  }

  .info-key {
    font-size: 0.82rem;
    color: var(--text-dim);
  }

  .info-val {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.82rem;
    color: var(--accent);
    font-weight: 500;
  }

  .geometry-name {
    font-size: 1.4rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    margin-bottom: 4px;
    background: linear-gradient(135deg, var(--accent), #66ffdd);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
  }

  .geometry-subtitle {
    font-size: 0.85rem;
    color: var(--text-dim);
    margin-bottom: 14px;
  }

  .formula-box {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.95rem;
    padding: 10px 14px;
    background: var(--bg);
    border-radius: var(--radius-sm);
    color: var(--warning);
    text-align: center;
    margin-bottom: 12px;
    border: 1px solid var(--border);
  }

  /* Angle badges */
  .angle-badges {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
    margin-top: 8px;
  }

  .angle-badge {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    padding: 4px 10px;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 20px;
    color: var(--text-dim);
  }

  /* Color picker */
  .color-options {
    display: flex;
    gap: 6px;
    flex-wrap: wrap;
  }

  .color-swatch {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    border: 2px solid transparent;
    cursor: pointer;
    transition: var(--transition);
  }

  .color-swatch:hover,
  .color-swatch.active {
    border-color: white;
    transform: scale(1.15);
  }

  /* Scrollbar */
  ::-webkit-scrollbar {
    width: 6px;
  }

  ::-webkit-scrollbar-track {
    background: transparent;
  }

  ::-webkit-scrollbar-thumb {
    background: var(--border);
    border-radius: 3px;
  }

  ::-webkit-scrollbar-thumb:hover {
    background: var(--text-muted);
  }

  /* Animation */
  @keyframes fadeIn {
    from {
      opacity: 0;
      transform: translateY(8px);
    }

    to {
      opacity: 1;
      transform: translateY(0);
    }
  }

  .section {
    animation: fadeIn 0.4s ease both;
  }

  .section:nth-child(2) {
    animation-delay: 0.05s;
  }

  .section:nth-child(3) {
    animation-delay: 0.1s;
  }

  .section:nth-child(4) {
    animation-delay: 0.15s;
  }

  .section:nth-child(5) {
    animation-delay: 0.2s;
  }

  /* Mobile adjustments */
  @media (max-width: 768px) {
    .header {
      padding: 12px 16px;
    }

    .header-brand h1 {
      font-size: 1rem;
    }

    .viewport {
      min-height: 50vh;
    }

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

  @media (max-width: 480px) {
    .preset-grid {
      grid-template-columns: 1fr 1fr;
    }
  }