:root {
    --bg: #191127;
    --surface: #23133a;
    --surface2: #1f1232;
    --border: #3a1c63;
    --accent: #883CF0;
    --accent2: #7c3aed;
    --warn: #7c3aed;
    --text: #e6edf3;
    --muted: #b29dce;
    --glow: rgba(151, 0, 245, 0.15);
  }
  *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
  html { scroll-behavior: smooth; }
  body {
    background: var(--bg);
    color: var(--text);
    font-family: 'DM Sans', sans-serif;
    min-height: 100vh;
    overflow-x: hidden;
  }

  /* ─── GRID OVERLAY ─── */
  body::before {
    content: '';
    position: fixed;
    inset: 0;
    background-image:
      linear-gradient(rgba(151, 0, 245, 0.03) 1px, transparent 1px),
      linear-gradient(90deg, rgba(196, 0, 245, 0.03) 1px, transparent 1px);
    background-size: 40px 40px;
    pointer-events: none;
    z-index: 0;
  }

  /* ─── NAV ─── */
  nav {
    position: fixed; top: 0; left: 0; right: 0; z-index: 100;
    display: flex; align-items: center; justify-content: space-between;
    padding: 0 2rem;
    height: 64px;
    background: #180f26;
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
  }
  .logo {
    font-family: 'Unbounded', sans-serif;
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--accent);
    letter-spacing: -0.02em;
  }
  .logo span { color: var(--muted); font-weight: 300; }
  nav ul { display: flex; gap: 2rem; list-style: none; }
  nav ul a {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    color: var(--muted);
    text-decoration: none;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    transition: color 0.2s;
  }
  nav ul a:hover { color: var(--accent); }
  .nav-badge {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.7rem;
    color: var(--accent);
    border: 1px solid var(--accent);
    padding: 4px 12px;
    border-radius: 2px;
  }

  /* ─── HERO ─── */
  .hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    padding: 8rem 4rem 4rem;
    overflow: hidden;
  }
  .hero-bg {
    position: absolute;
    inset: 0;
    background: radial-gradient(ellipse 60% 60% at 70% 50%, rgba(159, 0, 245, 0.07) 0%, transparent 60%),
                radial-gradient(ellipse 40% 40% at 20% 80%, rgba(174, 0, 255, 0.05) 0%, transparent 50%);
  }
  .hero-tag {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.7rem;
    color: var(--accent);
    letter-spacing: 0.15em;
    text-transform: uppercase;
    margin-bottom: 1.5rem;
    display: flex; align-items: center; gap: 0.75rem;
  }
  .hero-tag::before {
    content: '';
    width: 32px; height: 1px;
    background: var(--accent);
  }
  h1 {
    font-family: 'Unbounded', sans-serif;
    font-size: clamp(2.5rem, 6vw, 5.5rem);
    font-weight: 900;
    line-height: 0.95;
    letter-spacing: -0.03em;
    color: var(--text);
    margin-bottom: 2rem;
    position: relative;
  }
  h1 .accent-word { color: var(--accent); }
  h1 .accent2-word { color: var(--accent2); }
  .hero-sub {
    font-size: 1.1rem;
    color: var(--muted);
    max-width: 520px;
    line-height: 1.7;
    margin-bottom: 3rem;
  }
  .hero-cta {
    display: flex; gap: 1rem; flex-wrap: wrap;
  }
  .btn {
    display: inline-flex; align-items: center; gap: 0.5rem;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.8rem;
    font-weight: 500;
    letter-spacing: 0.05em;
    text-decoration: none;
    border: none; cursor: pointer;
    padding: 0.85rem 1.75rem;
    transition: all 0.2s;
  }
  .btn-primary {
    background: var(--accent);
    color: var(--bg);
    clip-path: polygon(0 0, calc(100% - 8px) 0, 100% 8px, 100% 100%, 8px 100%, 0 calc(100% - 8px));
  }
  .btn-primary:hover { background: #883cf0e0; transform: translateY(-2px); box-shadow: 0 8px 30px rgba(131, 0, 245, 0.3); }
  .btn-ghost {
    background: transparent;
    color: var(--text);
    border: 1px solid var(--border);
    clip-path: polygon(0 0, calc(100% - 8px) 0, 100% 8px, 100% 100%, 8px 100%, 0 calc(100% - 8px));
  }
  .btn-ghost:hover { border-color: var(--accent); color: var(--accent); }

  .hero-stats {
    position: absolute;
    right: 4rem; top: 50%;
    transform: translateY(-50%);
    display: flex; flex-direction: column; gap: 1.5rem;
  }
  .stat-card {
    background: var(--surface);
    border: 1px solid var(--border);
    padding: 1.25rem 1.5rem;
    min-width: 160px;
    position: relative;
    overflow: hidden;
  }
  .stat-card::before {
    content: '';
    position: absolute;
    left: 0; top: 0; bottom: 0;
    width: 3px;
    background: var(--accent);
  }
  .stat-num {
    font-family: 'Unbounded', sans-serif;
    font-size: 1.8rem;
    font-weight: 700;
    color: var(--accent);
    line-height: 1;
  }
  .stat-label {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.65rem;
    color: var(--muted);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin-top: 0.25rem;
  }

  /* ─── SECTION WRAPPER ─── */
  section {
    position: relative;
    padding: 5rem 4rem;
    z-index: 1;
  }
  .section-header {
    display: flex; align-items: baseline; gap: 1rem;
    margin-bottom: 3rem;
  }
  .section-num {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.7rem;
    color: var(--accent);
    border: 1px solid var(--accent);
    padding: 2px 8px;
    letter-spacing: 0.08em;
  }
  h2 {
    font-family: 'Unbounded', sans-serif;
    font-size: clamp(1.5rem, 3vw, 2.2rem);
    font-weight: 700;
    letter-spacing: -0.02em;
    color: var(--text);
  }
  .section-line {
    flex: 1;
    height: 1px;
    background: var(--border);
    max-width: 100px;
  }

  /* ─── DISCIPLINES ─── */
  .disciplines-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 1px;
    background: var(--border);
    border: 1px solid var(--border);
  }
  .disc-card {
    background: var(--surface);
    padding: 2rem 1.5rem;
    cursor: pointer;
    transition: all 0.25s;
    position: relative;
    overflow: hidden;
  }
  .disc-card::after {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(135deg, var(--glow), transparent);
    opacity: 0;
    transition: opacity 0.3s;
  }
  .disc-card:hover { background: var(--surface2); }
  .disc-card:hover::after { opacity: 1; }
  .disc-card.active {
    background: #1f1232;
    border: 1px solid var(--accent);
  }
  .disc-icon {
    font-size: 1.8rem;
    margin-bottom: 1rem;
    display: block;
  }
  .disc-name {
    font-family: 'Unbounded', sans-serif;
    font-size: 0.8rem;
    font-weight: 700;
    color: var(--text);
    margin-bottom: 0.5rem;
    letter-spacing: -0.01em;
  }
  .disc-count {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.65rem;
    color: var(--muted);
  }
  .disc-bar {
    margin-top: 1rem;
    height: 2px;
    background: var(--border);
    width: 100%;
  }
  .disc-fill {
    height: 100%;
    background: var(--accent);
    transition: width 0.6s ease;
  }

  /* ─── DETAIL PANEL ─── */
  #disc-detail {
    margin-top: 2rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-left: 3px solid var(--accent);
    padding: 2rem;
    display: none;
    animation: fadeSlide 0.3s ease;
  }
  @keyframes fadeSlide { from { opacity: 0; transform: translateY(-8px); } to { opacity: 1; transform: translateY(0); } }
  #disc-detail.show { display: grid; grid-template-columns: 1fr 1fr 1fr; gap: 2rem; }
  .detail-col h4 {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.65rem;
    color: var(--accent);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin-bottom: 0.75rem;
  }
  .detail-col ul { list-style: none; }
  .detail-col ul li {
    font-size: 0.85rem;
    color: var(--muted);
    padding: 0.3rem 0;
    border-bottom: 1px solid var(--border);
    display: flex; align-items: center; gap: 0.5rem;
    transition: color 0.2s;
  }
  .detail-col ul li:hover { color: var(--text); }
  .detail-col ul li::before { content: '→'; color: var(--accent); font-size: 0.7rem; }

  /* ─── CALCULATOR ─── */
  .calc-wrapper {
    display: grid;
    grid-template-columns: 260px 1fr;
    gap: 0;
    border: 1px solid var(--border);
    background: var(--border);
  }
  .calc-nav {
    background: var(--surface);
    padding: 0;
  }
  .calc-tab {
    display: flex; align-items: center; gap: 0.75rem;
    padding: 1.1rem 1.5rem;
    cursor: pointer;
    border-bottom: 1px solid var(--border);
    transition: all 0.2s;
    font-size: 0.85rem;
    color: var(--muted);
  }
  .calc-tab:hover { background: var(--surface2); color: var(--text); }
  .calc-tab.active {
    background: #2a1647;
    color: var(--accent);
    border-left: 3px solid var(--accent);
  }
  .calc-tab-icon { font-size: 1.1rem; }
  .calc-body { background: var(--surface2); padding: 2.5rem; }
  .calc-panel { display: none; }
  .calc-panel.active { display: block; animation: fadeSlide 0.2s ease; }
  .calc-title {
    font-family: 'Unbounded', sans-serif;
    font-size: 1.1rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    color: var(--text);
  }
  .calc-desc {
    font-size: 0.8rem;
    color: var(--muted);
    margin-bottom: 2rem;
    font-family: 'JetBrains Mono', monospace;
  }
  .form-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
    margin-bottom: 1rem;
  }
  .form-group { display: flex; flex-direction: column; gap: 0.4rem; }
  .form-group label {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.65rem;
    color: var(--muted);
    text-transform: uppercase;
    letter-spacing: 0.1em;
  }
  .form-group input, .form-group select {
    background: var(--surface);
    border: 1px solid var(--border);
    color: var(--text);
    padding: 0.7rem 1rem;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.85rem;
    outline: none;
    transition: border-color 0.2s;
    width: 100%;
  }
  .form-group input:focus, .form-group select:focus { border-color: var(--accent); }
  .form-group select option { background: var(--surface); }
  .calc-result {
    margin-top: 1.5rem;
    background: #2a1647;
    border: 1px solid #3a1c63;
    padding: 1.25rem;
    display: none;
  }
  .calc-result.show { display: block; animation: fadeSlide 0.2s ease; }
  .result-label {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.65rem;
    color: var(--accent);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin-bottom: 0.25rem;
  }
  .result-value {
    font-family: 'Unbounded', sans-serif;
    font-size: 1.8rem;
    font-weight: 700;
    color: var(--accent);
  }
  .result-unit {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    color: var(--muted);
    margin-top: 0.25rem;
  }

  /* ─── UNIT CONVERTER ─── */
  .converter-grid {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    align-items: center;
    gap: 1rem;
    margin-bottom: 1.5rem;
  }
  .arrow-center {
    font-family: 'JetBrains Mono', monospace;
    font-size: 1.2rem;
    color: var(--accent);
    text-align: center;
  }

  /* ─── RESOURCES ─── */
  .resources-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 1px;
    background: var(--border);
    border: 1px solid var(--border);
  }
  .resource-card {
    background: var(--surface);
    padding: 1.75rem;
    display: flex; flex-direction: column; gap: 0.75rem;
    transition: background 0.2s;
    cursor: pointer;
  }
  .resource-card:hover { background: var(--surface2); }
  .resource-meta {
    display: flex; align-items: center; gap: 0.75rem;
  }
  .resource-tag {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.6rem;
    padding: 2px 8px;
    text-transform: uppercase;
    letter-spacing: 0.08em;
  }
  .tag-civil { background: rgba(132, 0, 255, 0.1); color: var(--accent2); border: 1px solid rgba(132, 0, 255, 0.3); }
  .tag-mech { background: rgba(255,107,53,0.1); color: var(--warn); border: 1px solid rgba(255,107,53,0.3); }
  .tag-elec { background: rgba(0,245,160,0.1); color: var(--accent); border: 1px solid rgba(0,245,160,0.3); }
  .tag-software { background: rgba(155,89,182,0.1); color: #c39bd3; border: 1px solid rgba(155,89,182,0.3); }
  .tag-chem { background: rgba(255,200,0,0.1); color: #ffc800; border: 1px solid rgba(255,200,0,0.3); }
  .resource-date {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.6rem;
    color: var(--muted);
    margin-left: auto;
  }
  .resource-title {
    font-family: 'Unbounded', sans-serif;
    font-size: 0.9rem;
    font-weight: 700;
    color: var(--text);
    line-height: 1.3;
    letter-spacing: -0.01em;
  }
  .resource-excerpt {
    font-size: 0.8rem;
    color: var(--muted);
    line-height: 1.6;
  }
  .resource-footer {
    display: flex; align-items: center; justify-content: space-between;
    margin-top: auto; padding-top: 0.75rem;
    border-top: 1px solid var(--border);
  }
  .resource-author {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.65rem;
    color: var(--muted);
  }
  .resource-arrow {
    color: var(--accent);
    font-size: 0.9rem;
    transition: transform 0.2s;
  }
  .resource-card:hover .resource-arrow { transform: translateX(4px); }

  /* ─── SEARCH ─── */
  .search-bar {
    display: flex; gap: 0;
    margin-bottom: 2rem;
    border: 1px solid var(--border);
    background: var(--surface);
  }
  .search-bar input {
    flex: 1;
    background: none;
    border: none;
    color: var(--text);
    padding: 0.9rem 1.25rem;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.85rem;
    outline: none;
  }
  .search-bar input::placeholder { color: var(--muted); }
  .search-bar button {
    background: var(--accent);
    border: none;
    color: var(--bg);
    padding: 0 1.5rem;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.05em;
    cursor: pointer;
    text-transform: uppercase;
    transition: background 0.2s;
  }
  .search-bar button:hover { background: #883cf0e0; }
  .filter-row { display: flex; gap: 0.5rem; flex-wrap: wrap; margin-bottom: 2rem; }
  .filter-chip {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.65rem;
    padding: 4px 12px;
    border: 1px solid var(--border);
    color: var(--muted);
    cursor: pointer;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    transition: all 0.2s;
    background: none;
  }
  .filter-chip:hover, .filter-chip.active { border-color: var(--accent); color: var(--accent); background: #2a1647; }

  /* ─── FORMULA DB ─── */
  .formula-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1rem;
  }
  .formula-card {
    background: var(--surface);
    border: 1px solid var(--border);
    padding: 1.5rem;
    transition: border-color 0.2s, transform 0.2s;
  }
  .formula-card:hover { border-color: var(--accent); transform: translateY(-2px); }
  .formula-cat {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.6rem;
    color: var(--accent);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin-bottom: 0.5rem;
  }
  .formula-name {
    font-family: 'Unbounded', sans-serif;
    font-size: 0.85rem;
    font-weight: 700;
    color: var(--text);
    margin-bottom: 1rem;
  }
  .formula-expr {
    background: var(--bg);
    border: 1px solid var(--border);
    padding: 0.75rem 1rem;
    font-family: 'JetBrains Mono', monospace;
    font-size: 1rem;
    color: var(--accent2);
    margin-bottom: 0.75rem;
    text-align: center;
    letter-spacing: 0.05em;
  }
  .formula-desc { font-size: 0.78rem; color: var(--muted); line-height: 1.5; }

  /* ─── FOOTER ─── */
  footer {
    border-top: 1px solid var(--border);
    padding: 2rem 4rem;
    display: flex; align-items: center; justify-content: space-between;
  }
  footer .logo { font-size: 0.9rem; }
  .footer-links { display: flex; gap: 2rem; }
  .footer-links a {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.65rem;
    color: var(--muted);
    text-decoration: none;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    transition: color 0.2s;
  }
  .footer-links a:hover { color: var(--accent); }
  .footer-copy {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.65rem;
    color: var(--muted);
  }

  /* ─── TICKER ─── */
  .ticker-wrap {
    overflow: hidden;
    background: var(--surface);
    border-top: 1px solid var(--border);
    border-bottom: 1px solid var(--border);
    padding: 0.6rem 0;
  }
  .ticker-track {
    display: flex; gap: 3rem;
    width: max-content;
    animation: ticker 30s linear infinite;
  }
  @keyframes ticker { from { transform: translateX(0); } to { transform: translateX(-50%); } }
  .ticker-item {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.65rem;
    color: var(--muted);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    white-space: nowrap;
    display: flex; gap: 0.5rem; align-items: center;
  }
  .ticker-item .dot { color: var(--accent); }

  /* ─── RESPONSIVE ─── */
  @media (max-width: 1024px) {
    .hero-stats { display: none; }
    .hero { padding: 7rem 2rem 3rem; }
    section { padding: 4rem 2rem; }
    .calc-wrapper { grid-template-columns: 1fr; }
    .calc-nav { display: flex; flex-wrap: wrap; }
    .calc-tab { border-bottom: none; border-right: 1px solid var(--border); }
    footer { padding: 2rem; flex-direction: column; gap: 1rem; }
    nav ul { display: none; }
    #disc-detail.show { grid-template-columns: 1fr; }
  }
  @media (max-width: 640px) {
    .form-row { grid-template-columns: 1fr; }
    .converter-grid { grid-template-columns: 1fr; }
  }

  /* ─── SCROLL ANIMATIONS ─── */
  .reveal {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.6s ease, transform 0.6s ease;
  }
  .reveal.visible { opacity: 1; transform: translateY(0); }