:root {
      --bg: #f1f5f9;
      --surface: #ffffff;
      --border: #e2e8f0;
      --text: #1e293b;
      --muted: #64748b;
      --primary: #3b82f6;
      --primary-hover: #2563eb;
      --danger-bg: #fef2f2;
      --danger-border: #fecaca;
      --danger-text: #b91c1c;
      --cell-size: 56px;
    }

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

    body {
      font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      background: var(--bg);
      color: var(--text);
      min-height: 100vh;
      padding: 2rem 1rem;
    }

    .container { max-width: 860px; margin: 0 auto; }

    header { margin-bottom: 2rem; }
    header h1 { font-size: 2rem; font-weight: 800; letter-spacing: -0.02em; }
    header p { color: var(--muted); margin-top: 0.35rem; }

    .card {
      background: var(--surface);
      border: 1px solid var(--border);
      border-radius: 14px;
      padding: 1.5rem;
      margin-bottom: 1.5rem;
      box-shadow: 0 1px 3px rgba(0,0,0,0.06);
    }
    .card h2 { font-size: 1rem; font-weight: 600; margin-bottom: 1rem; color: var(--muted); text-transform: uppercase; letter-spacing: 0.06em; }

    textarea {
      width: 100%;
      min-height: 130px;
      padding: 0.75rem 1rem;
      border: 1.5px solid var(--border);
      border-radius: 8px;
      font-size: 1rem;
      font-family: 'Menlo', 'Consolas', monospace;
      resize: vertical;
      color: var(--text);
      background: var(--bg);
      transition: border-color 0.15s, box-shadow 0.15s;
    }
    textarea:focus {
      outline: none;
      border-color: var(--primary);
      box-shadow: 0 0 0 3px rgba(59,130,246,0.15);
    }

    .input-row {
      display: flex;
      gap: 0.75rem;
      align-items: flex-start;
      margin-top: 0.75rem;
      flex-wrap: wrap;
    }

    button {
      padding: 0.6rem 1.4rem;
      background: var(--primary);
      color: #fff;
      border: none;
      border-radius: 8px;
      font-size: 0.95rem;
      font-weight: 600;
      cursor: pointer;
      transition: background 0.15s;
      white-space: nowrap;
    }
    button:hover { background: var(--primary-hover); }
    button:active { opacity: 0.85; }
    #print-btn {
      background: #475569;
      display: none;
    }
    #print-btn:hover { background: #334155; }

    #error-msg {
      display: none;
      background: var(--danger-bg);
      border: 1px solid var(--danger-border);
      color: var(--danger-text);
      padding: 0.7rem 1rem;
      border-radius: 8px;
      font-size: 0.9rem;
      flex: 1 1 100%;
    }

    #output { display: none; }
    #output.visible { display: block; }

    .output-layout {
      display: flex;
      gap: 2rem;
      flex-wrap: wrap;
      align-items: flex-start;
    }

    /* Grid */
    .grid-wrap { flex-shrink: 0; }

    /*
     * Layout: start-box sits above col 2, end-box sits right of row 2.
     * Total size = 6 cells + 5 gaps in each dimension (a perfect square).
     *   width  = 6*cell + 5*5px
     *   height = same
     */
    .puzzle-area {
      position: relative;
      width: calc(6 * var(--cell-size) + 25px);
      height: calc(6 * var(--cell-size) + 25px);
    }

    .grid {
      position: absolute;
      top: calc(var(--cell-size) + 5px);
      left: 0;
      display: grid;
      grid-template-columns: repeat(5, var(--cell-size));
      gap: 5px;
    }

    .start-box,
    .end-box {
      position: absolute;
      width: var(--cell-size);
      height: var(--cell-size);
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 1px;
      border: 2px solid #94a3b8;
      border-radius: 50%;
      background: #f8fafc;
      color: var(--muted);
      transform: scale(0.72);
    }
    /* above col 2 */
    .start-box {
      left: calc(2 * (var(--cell-size) + 5px));
      top: 0;
    }
    /* right of col 4, vertically aligned with row 2 */
    .end-box {
      left: calc(5 * (var(--cell-size) + 5px));
      top: calc(3 * (var(--cell-size) + 5px));
    }

    .box-symbol { font-size: 1.1rem; line-height: 1; }
    .box-label  { font-size: 0.55rem; text-transform: uppercase; letter-spacing: 0.07em; }

    #word-path {
      position: absolute;
      top: 0; left: 0;
      width: 100%; height: 100%;
      pointer-events: none;
      overflow: visible;
    }

    .cell {
      width: var(--cell-size);
      height: var(--cell-size);
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 1.25rem;
      font-weight: 800;
      font-family: 'Menlo', 'Consolas', monospace;
      border-radius: 50%;
      border: 2px solid transparent;
      background: var(--bg);
      color: var(--text);
      transform: scale(0.72);
      transition: background 0.2s, color 0.2s, box-shadow 0.2s, transform 0.15s;
      cursor: default;
      user-select: none;
    }
    .grid-hint {
      font-size: 0.78rem;
      color: var(--muted);
      margin-top: 0.6rem;
    }

    /* Word list */
    .word-list {
      flex: 1;
      min-width: 220px;
      display: flex;
      flex-direction: column;
      gap: 0.5rem;
    }

    .word-card {
      padding: 0.65rem 0.9rem;
      border-radius: 9px;
      cursor: pointer;
      border: 2px solid transparent;
      transition: opacity 0.15s, border-color 0.15s;
    }
    .word-card:hover { opacity: 0.85; }
    .word-card.selected { border-color: rgba(0,0,0,0.25); }

    .word-name {
      font-size: 1rem;
      font-weight: 700;
      font-family: 'Menlo', 'Consolas', monospace;
      letter-spacing: 0.15em;
    }
    .word-meta {
      font-size: 0.78rem;
      margin-top: 0.25rem;
      opacity: 0.75;
    }
    .word-positions {
      font-size: 0.78rem;
      margin-top: 0.15rem;
      font-family: 'Menlo', 'Consolas', monospace;
      opacity: 0.7;
      word-break: break-all;
    }
    .word-directions {
      display: none;
      font-size: 0.72rem;
      margin-top: 0.4rem;
      font-family: 'Menlo', 'Consolas', monospace;
      opacity: 0.8;
      line-height: 1.6;
      white-space: pre;
    }
    .word-card.selected .word-directions { display: block; }

    /* Coordinate tooltip */
    .coord-label {
      display: flex;
      gap: 1.5rem;
      font-size: 0.75rem;
      color: var(--muted);
      margin-top: 0.3rem;
    }

    /* Toggle switch */
    .toggle-label {
      display: inline-flex;
      align-items: center;
      gap: 0.5rem;
      cursor: pointer;
      font-size: 0.82rem;
      color: var(--muted);
      user-select: none;
      margin-top: 0.6rem;
    }
    .toggle-label input[type="checkbox"] {
      position: absolute;
      opacity: 0;
      width: 0;
      height: 0;
    }
    .toggle-track {
      width: 36px;
      height: 20px;
      background: #cbd5e1;
      border-radius: 10px;
      position: relative;
      flex-shrink: 0;
      transition: background 0.2s;
    }
    .toggle-track::after {
      content: '';
      position: absolute;
      width: 16px;
      height: 16px;
      background: white;
      border-radius: 50%;
      top: 2px;
      left: 2px;
      transition: left 0.2s;
      box-shadow: 0 1px 2px rgba(0,0,0,0.2);
    }
    .toggle-label input:checked + .toggle-track { background: var(--primary); }
    .toggle-label input:checked + .toggle-track::after { left: 18px; }

    @media (max-width: 520px) {
      :root { --cell-size: 46px; }
      header h1 { font-size: 1.5rem; }
    }