:root {
    --bg: #0a0d0f;
    --surface: #111518;
    --panel: #161b1f;
    --border: #1e2a32;
    --accent: #00e5ff;
    --accent2: #ff6b35;
    --green: #39ff14;
    --yellow: #ffe135;
    --text: #cdd9e5;
    --muted: #5a7080;
    --cell-size: 64px;
    --font-mono: 'Share Tech Mono', monospace;
    --font-ui: 'Exo 2', sans-serif;
  }

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

  body {
    background: var(--bg);
    color: var(--text);
    font-family: var(--font-ui);
    min-height: 100vh;
    overflow-x: hidden;
  }

  /* grid bg */
  body::before {
    content: '';
    position: fixed; inset: 0;
    background-image:
      linear-gradient(var(--border) 1px, transparent 1px),
      linear-gradient(90deg, var(--border) 1px, transparent 1px);
    background-size: 40px 40px;
    opacity: 0.4;
    pointer-events: none;
    z-index: 0;
  }

  .container {
    position: relative; z-index: 1;
    max-width: 960px;
    margin: 0 auto;
    padding: 32px 20px 60px;
  }

  header {
    display: flex; align-items: center; gap: 16px;
    margin-bottom: 40px;
    border-bottom: 1px solid var(--border);
    padding-bottom: 24px;
  }

  .logo-icon {
    width: 48px; height: 48px;
    border: 2px solid var(--accent);
    display: grid; grid-template-columns: 1fr 1fr; gap: 3px;
    padding: 6px;
    box-shadow: 0 0 16px rgba(0,229,255,0.3);
  }
  .logo-icon span {
    background: var(--accent);
    display: block;
  }
  .logo-icon span:nth-child(2), .logo-icon span:nth-child(3) {
    background: transparent;
    border: 1px solid var(--accent);
  }

  header h1 {
    font-size: 28px; font-weight: 800;
    letter-spacing: -0.5px;
    color: #fff;
  }
  header h1 em {
    font-style: normal;
    color: var(--accent);
  }
  header p {
    font-size: 13px;
    color: var(--muted);
    font-family: var(--font-mono);
    margin-top: 2px;
  }

  /* CONTROLS */
  .controls {
    background: var(--surface);
    border: 1px solid var(--border);
    padding: 24px;
    margin-bottom: 24px;
  }

  .control-row {
    display: flex; align-items: center; gap: 16px; flex-wrap: wrap;
    margin-bottom: 16px;
  }
  .control-row:last-child { margin-bottom: 0; }

  label {
    font-size: 12px; font-weight: 600;
    letter-spacing: 1.5px; text-transform: uppercase;
    color: var(--muted);
    min-width: 80px;
  }

  select, input[type="text"] {
    background: var(--panel);
    border: 1px solid var(--border);
    color: var(--text);
    font-family: var(--font-mono);
    font-size: 14px;
    padding: 8px 12px;
    outline: none;
    transition: border-color 0.2s;
  }
  select:focus, input[type="text"]:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 1px var(--accent);
  }

  .var-select { display: flex; gap: 8px; }

  .btn {
    font-family: var(--font-ui);
    font-size: 13px; font-weight: 600;
    letter-spacing: 1px; text-transform: uppercase;
    padding: 10px 24px;
    border: none; cursor: pointer;
    transition: all 0.15s;
    position: relative; overflow: hidden;
  }
  .btn-primary {
    background: var(--accent);
    color: #000;
  }
  .btn-primary:hover {
    background: #fff;
    box-shadow: 0 0 20px rgba(0,229,255,0.5);
  }
  .btn-secondary {
    background: transparent;
    color: var(--muted);
    border: 1px solid var(--border);
  }
  .btn-secondary:hover {
    color: var(--text);
    border-color: var(--muted);
  }
  .btn-orange {
    background: var(--accent2);
    color: #fff;
  }
  .btn-orange:hover {
    background: #ff8c5a;
    box-shadow: 0 0 20px rgba(255,107,53,0.4);
  }

  /* MINTERM input */
  .minterm-input {
    flex: 1; min-width: 200px;
  }

  /* INFO STRIP */
  .info-strip {
    display: flex; gap: 0;
    border: 1px solid var(--border);
    margin-bottom: 24px;
    overflow: hidden;
  }
  .info-item {
    flex: 1;
    background: var(--surface);
    padding: 12px 16px;
    border-right: 1px solid var(--border);
    font-size: 12px;
  }
  .info-item:last-child { border-right: none; }
  .info-item .lbl { color: var(--muted); font-family: var(--font-mono); }
  .info-item .val { color: var(--accent); font-weight: 700; font-family: var(--font-mono); font-size: 14px; }

  /* KMAP AREA */
  .kmap-wrap {
    display: flex; gap: 24px; flex-wrap: wrap;
    margin-bottom: 24px;
  }

  .kmap-section {
    background: var(--surface);
    border: 1px solid var(--border);
    padding: 24px;
    flex: 1; min-width: 300px;
  }

  .section-title {
    font-size: 11px; font-weight: 600;
    letter-spacing: 2px; text-transform: uppercase;
    color: var(--muted);
    margin-bottom: 20px;
    display: flex; align-items: center; gap: 8px;
  }
  .section-title::after {
    content: '';
    flex: 1; height: 1px;
    background: var(--border);
  }

  /* KMAP TABLE */
  .kmap-table-wrap {
    overflow-x: auto;
  }

  .kmap-table {
    border-collapse: collapse;
    font-family: var(--font-mono);
  }

  .kmap-table th {
    background: var(--panel);
    color: var(--accent);
    font-size: 13px;
    padding: 0 12px;
    height: 44px;
    text-align: center;
    border: 1px solid var(--border);
    min-width: var(--cell-size);
    font-weight: 400;
  }

  .kmap-table th.corner {
    background: transparent;
    border: none;
    position: relative;
  }
  .kmap-table th.corner::after {
    content: '';
    position: absolute;
    top: 50%; left: 0; right: 0;
    height: 1px; background: var(--border);
    transform: rotate(-30deg);
  }

  .kmap-table td {
    width: var(--cell-size); height: var(--cell-size);
    text-align: center; vertical-align: middle;
    border: 1px solid var(--border);
    font-size: 18px; font-weight: 700;
    cursor: pointer;
    transition: background 0.15s, color 0.15s;
    position: relative;
    user-select: none;
  }

  .kmap-table td.val-0 {
    background: var(--panel);
    color: var(--muted);
  }
  .kmap-table td.val-1 {
    background: rgba(0,229,255,0.08);
    color: var(--accent);
    box-shadow: inset 0 0 12px rgba(0,229,255,0.15);
  }
  .kmap-table td.val-x {
    background: rgba(255,225,53,0.06);
    color: var(--yellow);
  }

  .kmap-table td:hover {
    background: rgba(0,229,255,0.2) !important;
    color: #fff !important;
  }

  /* Group overlays */
  .kmap-table td.grouped {
    outline: 2px solid var(--accent2);
    outline-offset: -2px;
  }

  .group-badge {
    position: absolute;
    top: 2px; right: 3px;
    font-size: 9px;
    color: var(--accent2);
    font-weight: 700;
    line-height: 1;
  }

  /* RESULT PANEL */
  .result-panel {
    background: var(--surface);
    border: 1px solid var(--border);
    padding: 24px;
    margin-bottom: 24px;
  }

  .expression-display {
    background: var(--panel);
    border: 1px solid var(--border);
    border-left: 3px solid var(--accent);
    padding: 16px 20px;
    margin-bottom: 16px;
    font-family: var(--font-mono);
    font-size: 20px;
    color: #fff;
    letter-spacing: 1px;
    min-height: 60px;
    display: flex; align-items: center;
  }

  .expression-display.empty {
    color: var(--muted);
    font-size: 14px;
  }

  .groups-list {
    display: flex; flex-wrap: wrap; gap: 8px;
    margin-top: 12px;
  }

  .group-tag {
    background: rgba(255,107,53,0.1);
    border: 1px solid var(--accent2);
    color: var(--accent2);
    font-family: var(--font-mono);
    font-size: 13px;
    padding: 4px 10px;
    display: flex; align-items: center; gap: 6px;
  }
  .group-tag .dot {
    width: 8px; height: 8px;
    background: var(--accent2);
    flex-shrink: 0;
  }

  /* TRUTH TABLE */
  .truth-table {
    width: 100%;
    border-collapse: collapse;
    font-family: var(--font-mono);
    font-size: 13px;
  }
  .truth-table th {
    background: var(--panel);
    color: var(--accent);
    padding: 8px 16px;
    text-align: center;
    border: 1px solid var(--border);
    font-weight: 400;
    letter-spacing: 1px;
  }
  .truth-table td {
    text-align: center;
    padding: 7px 16px;
    border: 1px solid var(--border);
    color: var(--muted);
  }
  .truth-table tr:nth-child(even) td { background: rgba(255,255,255,0.02); }
  .truth-table td.one { color: var(--accent); font-weight: 700; }
  .truth-table td.dc { color: var(--yellow); }
  .truth-table td.minterm-idx { color: var(--muted); font-size: 11px; }

  /* TOGGLE BTNS */
  .tab-bar {
    display: flex; gap: 0;
    border: 1px solid var(--border);
    overflow: hidden;
    margin-bottom: 24px;
    width: fit-content;
  }
  .tab-btn {
    background: var(--panel);
    color: var(--muted);
    border: none;
    font-family: var(--font-ui);
    font-size: 12px; font-weight: 600;
    letter-spacing: 1px; text-transform: uppercase;
    padding: 10px 20px;
    cursor: pointer;
    border-right: 1px solid var(--border);
    transition: all 0.15s;
  }
  .tab-btn:last-child { border-right: none; }
  .tab-btn.active {
    background: var(--accent);
    color: #000;
  }
  .tab-btn:not(.active):hover {
    background: var(--surface);
    color: var(--text);
  }

  /* MODE SELECTOR */
  .mode-btns { display: flex; gap: 8px; }
  .mode-btn {
    background: var(--panel);
    color: var(--muted);
    border: 1px solid var(--border);
    font-family: var(--font-mono);
    font-size: 12px;
    padding: 6px 14px;
    cursor: pointer;
    transition: all 0.15s;
  }
  .mode-btn.active {
    background: rgba(0,229,255,0.1);
    color: var(--accent);
    border-color: var(--accent);
  }

  /* STEP LOG */
  .step-log {
    background: var(--panel);
    border: 1px solid var(--border);
    padding: 16px;
    font-family: var(--font-mono);
    font-size: 12px;
    color: var(--muted);
    max-height: 200px;
    overflow-y: auto;
    line-height: 1.8;
  }
  .step-log .step-line { display: block; }
  .step-log .step-line.hi { color: var(--green); }
  .step-log .step-line.warn { color: var(--yellow); }

  .hidden { display: none !important; }

  /* SCAN ANIMATION */
  @keyframes scanline {
    0% { transform: translateY(-100%); }
    100% { transform: translateY(100vh); }
  }
  .scanline {
    position: fixed;
    top: 0; left: 0; right: 0;
    height: 2px;
    background: linear-gradient(transparent, var(--accent), transparent);
    opacity: 0.15;
    animation: scanline 4s linear infinite;
    pointer-events: none;
    z-index: 9999;
  }

  @keyframes pulse-border {
    0%, 100% { box-shadow: 0 0 0 0 rgba(0,229,255,0.4); }
    50% { box-shadow: 0 0 0 4px rgba(0,229,255,0); }
  }
  .pulse { animation: pulse-border 1.5s ease-in-out 3; }