:root {
      --bg: #f6f8fc;
      --card: #ffffff;
      --ink: #1f2a44;
      --sub: #5f6b85;
      --line: #dde4f0;
      --blue: #4f7cff;
      --blue-soft: #eaf0ff;
      --orange: #ff9b55;
      --orange-soft: #fff1e7;
      --green: #1ea672;
      --yellow: #c28d12;
      --red: #dd5252;
      --shadow: 0 14px 34px rgba(31, 42, 68, 0.08);
      --radius: 22px;
    }

    * { box-sizing: border-box; }

    body {
      margin: 0;
      background: linear-gradient(180deg, #f8fbff 0%, #f6f8fc 100%);
      color: var(--ink);
      font-family: "Inter", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
    }

    .app {
      max-width: 1360px;
      margin: 0 auto;
      padding: 28px 18px 48px;
    }

    .hero {
      padding: 16px 18px;
      border-radius: 28px;
      color: #fff;
      background: linear-gradient(135deg, #3d63f3 0%, #4f7cff 45%, #6a92ff 100%);
      box-shadow: 0 18px 42px rgba(79, 124, 255, 0.28);
      position: relative;
      overflow: hidden;
    }

    .hero::after {
      content: "";
      position: absolute;
      right: -70px;
      top: -50px;
      width: 240px;
      height: 240px;
      background: radial-gradient(circle, rgba(255,255,255,0.24), rgba(255,255,255,0));
      border-radius: 50%;
    }

    .hero h1 {
      margin: 0;
      font-size: clamp(14px, 4vw, 28px);
      letter-spacing: 0.2px;
    }

    .hero p {
      margin: 10px 0 0;
      max-width: 980px;
      line-height: 1.7;
      color: rgba(255,255,255,0.92);
      font-size: 15px;
    }

    .hero-badges {
      margin-top: 16px;
      display: flex;
      flex-wrap: wrap;
      gap: 10px;
    }

    .badge {
      padding: 8px 12px;
      border-radius: 999px;
      font-size: 13px;
      background: rgba(255,255,255,0.16);
      border: 1px solid rgba(255,255,255,0.18);
      backdrop-filter: blur(4px);
    }

    .card {
      background: var(--card);
      border-radius: var(--radius);
      box-shadow: var(--shadow);
      border: 1px solid rgba(221, 228, 240, 0.88);
    }

    .controls {
      margin-top: 18px;
      padding: 22px;
    }

    .controls-line {
      display: flex;
      align-items: center;
      gap: 14px;
      flex-wrap: wrap;
    }

    .control-group {
      display: inline-flex;
      align-items: center;
      gap: 10px;
      flex-wrap: nowrap;
      width: 100%;
      justify-content: space-between;
    }

    .field.inline {
      display: inline-flex;
      align-items: center;
      gap: 8px;
      min-width: 0;
      flex: 1 1 0;
    }

    .field.inline label {
      margin: 0;
      white-space: nowrap;
    }

    .field.inline input,
    .field.inline select {
      width: 96px;
      height: 38px;
      padding: 0 10px;
      border-radius: 12px;
      font-size: 14px;
    }

    .field label,
    .toggle-group .title,
    .button-panel .title,
    .scale-panel .title {
      display: block;
      font-size: 13px;
      color: var(--sub);
      margin-bottom: 8px;
      font-weight: 600;
    }

    .field input,
    .field select {
      width: 100%;
      height: 44px;
      padding: 0 12px;
      border-radius: 14px;
      border: 1px solid var(--line);
      background: #fbfcff;
      color: var(--ink);
      font-size: 15px;
      outline: none;
      transition: 0.2s ease;
    }

    .field input:focus,
    .field select:focus {
      border-color: var(--blue);
      box-shadow: 0 0 0 4px rgba(79,124,255,0.12);
    }

    .button-panel,
    .toggle-group,
    .scale-panel {
      margin-top: 16px;
    }

    .controls-line .button-panel,
    .controls-line .scale-panel {
      margin-top: 0;
    }

    .controls-line .title {
      display: none;
    }

    .btn-row,
    .toggle-row,
    .preset-row,
    .scale-row {
      display: flex;
      flex-wrap: wrap;
      gap: 10px;
    }

    button {
      border: none;
      cursor: pointer;
      transition: 0.18s ease;
      font-family: inherit;
    }

    .btn {
      height: 42px;
      padding: 0 16px;
      border-radius: 14px;
      background: #f0f4ff;
      color: var(--ink);
      font-weight: 700;
      font-size: 14px;
      border: 1px solid transparent;
    }

    .btn:hover { transform: translateY(-1px); }
    .btn:disabled { cursor: not-allowed; opacity: 0.55; transform: none; }

    .btn.primary {
      background: linear-gradient(135deg, #4f7cff 0%, #6289ff 100%);
      color: #fff;
      box-shadow: 0 10px 20px rgba(79, 124, 255, 0.22);
    }

    .btn.warm {
      background: linear-gradient(135deg, #ff9b55 0%, #ffb36e 100%);
      color: #fff;
      box-shadow: 0 10px 20px rgba(255, 155, 85, 0.22);
    }

    .btn.ghost {
      background: #fff;
      border: 1px solid var(--line);
    }

    .btn.subtle-blue { background: var(--blue-soft); color: var(--blue); }
    .btn.subtle-orange { background: var(--orange-soft); color: #d8732d; }

    .toggle-pill {
      display: inline-flex;
      align-items: center;
      gap: 8px;
      padding: 10px 12px;
      background: #f8faff;
      border: 1px solid var(--line);
      border-radius: 14px;
      font-size: 14px;
      color: var(--ink);
      user-select: none;
    }

    .toggle-pill input { accent-color: var(--blue); }

    .status-strip {
      margin-top: 16px;
      display: grid;
      grid-template-columns: repeat(4, minmax(0, 1fr));
      gap: 12px;
    }

    .metric {
      padding: 16px 18px;
      border-radius: 18px;
      background: #fbfcff;
      border: 1px solid var(--line);
      min-height: 90px;
    }

    .metric .label {
      font-size: 13px;
      color: var(--sub);
      margin-bottom: 8px;
      font-weight: 600;
    }

    .metric .value {
      font-size: 22px;
      font-weight: 800;
      letter-spacing: 0.2px;
    }

    .metric .hint {
      margin-top: 7px;
      font-size: 13px;
      color: var(--sub);
      line-height: 1.5;
    }

    .metric.good .value { color: var(--green); }
    .metric.mid .value { color: var(--yellow); }
    .metric.warn .value { color: var(--red); }

    .concept-grid,
    .summary-grid,
    .chart-2col,
    .sim-grid {
      display: grid;
      gap: 16px;
      margin-top: 18px;
    }

    .concept-grid {
      grid-template-columns: repeat(4, minmax(0, 1fr));
    }

    .concept-card,
    .summary-card {
      padding: 18px 18px 16px;
    }

    .concept-card h3,
    .summary-card h3,
    .panel h3,
    .chart-card h3,
    .table-card h3 {
      margin: 0 0 10px;
      font-size: 18px;
    }

    .concept-card p,
    .summary-card p,
    .panel p,
    .chart-card p,
    .table-card p {
      margin: 0;
      color: var(--sub);
      line-height: 1.7;
      font-size: 14px;
    }

    .concept-card .tag,
    .panel .tag {
      display: inline-flex;
      align-items: center;
      padding: 6px 10px;
      border-radius: 999px;
      font-size: 12px;
      font-weight: 700;
      margin-bottom: 12px;
    }

    .tag.blue { background: var(--blue-soft); color: var(--blue); }
    .tag.orange { background: var(--orange-soft); color: #d8732d; }
    .tag.green { background: rgba(30,166,114,0.12); color: var(--green); }
    .tag.red { background: rgba(221,82,82,0.12); color: var(--red); }

    .sim-grid {
      grid-template-columns: repeat(2, minmax(0, 1fr));
    }

    .panel {
      padding: 20px;
      min-height: 560px;
      display: flex;
      flex-direction: column;
    }

    .panel-head {
      display: flex;
      align-items: flex-start;
      justify-content: space-between;
      gap: 12px;
      margin-bottom: 14px;
    }

    .bag-shell {
      border-radius: 22px;
      background: linear-gradient(180deg, #fcfdff 0%, #f3f7ff 100%);
      border: 1px solid #dfe7f5;
      padding: 16px;
    }

    .bag-title {
      font-size: 13px;
      font-weight: 700;
      color: var(--sub);
      margin-bottom: 10px;
      display: flex;
      justify-content: space-between;
      align-items: center;
      gap: 10px;
    }

    .bag-grid {
      min-height: 0;
      display: grid;
      grid-template-columns: repeat(20, 1fr);
      gap: 4px;
      align-content: start;
      padding: 6px 2px 2px;
    }

    .ball {
      width: 100%;
      aspect-ratio: 1 / 1;
      border-radius: 50%;
      box-shadow: inset 0 -4px 7px rgba(0, 0, 0, 0.08), 0 2px 6px rgba(0,0,0,0.08);
      border: 1px solid rgba(31,42,68,0.08);
      transition: transform 0.18s ease;
    }

    .ball:hover { transform: translateY(-1px); }
    .ball.white { background: radial-gradient(circle at 35% 30%, #ffffff, #f2f4f9 70%, #d9dde6 100%); }
    .ball.black { background: radial-gradient(circle at 35% 30%, #727b94, #2b3347 68%, #161d2c 100%); }
    .ball.drawn {
      transform: scale(1.08);
      outline: 3px solid rgba(255, 184, 76, 0.9);
      box-shadow: 0 0 0 3px rgba(255, 184, 76, 0.28), 0 0 18px rgba(255, 184, 76, 0.52);
      animation: ballFlash 0.28s ease;
    }

    @keyframes ballFlash {
      0% { transform: scale(0.95); }
      100% { transform: scale(1.08); }
    }

    .bag-meta {
      display: flex;
      justify-content: space-between;
      gap: 12px;
      flex-wrap: wrap;
      margin-top: 10px;
      color: var(--sub);
      font-size: 16px;
    }

    .current-wrap {
      display: grid;
      grid-template-columns: 96px 1fr;
      gap: 12px;
      margin-top: 16px;
      align-items: center;
    }

    .current-ball {
      width: 74px;
      height: 74px;
      border-radius: 50%;
      margin: 0 auto;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 20px;
      font-weight: 800;
      letter-spacing: 1px;
      border: 1px solid rgba(31,42,68,0.08);
      box-shadow: inset 0 -6px 10px rgba(0,0,0,0.08), 0 10px 22px rgba(0,0,0,0.08);
      animation: pop 0.35s ease;
    }

    .current-ball.white { background: radial-gradient(circle at 35% 30%, #ffffff, #eef3ff 70%, #dbe1ee 100%); color: #6a7896; }
    .current-ball.black { background: radial-gradient(circle at 35% 30%, #77829d, #1f2940 68%, #121b2b 100%); color: #ffffff; }
    .current-ball.idle { background: linear-gradient(135deg, #eef3ff, #e6ecfb); color: #7d8aa7; }

    @keyframes pop {
      0% { transform: scale(0.8); opacity: 0.4; }
      100% { transform: scale(1); opacity: 1; }
    }

    .sample-shell {
      margin-top: 16px;
      padding: 14px;
      border-radius: 18px;
      background: #fbfcff;
      border: 1px solid var(--line);
    }

    .sample-top {
      display: flex;
      justify-content: space-between;
      align-items: center;
      margin-bottom: 10px;
      gap: 10px;
    }

    .sample-top strong {
      font-size: 14px;
    }

    .sample-row {
      display: flex;
      flex-wrap: wrap;
      gap: 10px;
      min-height: 78px;
      align-content: flex-start;
      padding-top: 4px;
    }

    .draw-chip {
      width: 30px;
      height: 30px;
      border-radius: 50%;
      display: flex;
      align-items: center;
      justify-content: center;
      font-weight: 700;
      font-size: 11px;
      border: 1px solid rgba(31,42,68,0.08);
      box-shadow: inset 0 -3px 6px rgba(0,0,0,0.08), 0 2px 6px rgba(31,42,68,0.08);
    }

    .draw-chip.pending {
      background: radial-gradient(circle at 35% 30%, #ffffff, #f2f4f9 70%, #d9dde6 100%);
      color: #9ba7c0;
      border-style: dashed;
    }

    .draw-chip.white {
      background: radial-gradient(circle at 35% 30%, #ffffff, #eef3ff 70%, #dbe1ee 100%);
      color: transparent;
    }

    .draw-chip.black {
      background: radial-gradient(circle at 35% 30%, #77829d, #1f2940 68%, #121b2b 100%);
      color: transparent;
    }

    .draw-chip.active { outline: 3px solid rgba(79,124,255,0.22); transform: translateY(-1px); }

    .stats-grid {
      margin-top: 16px;
      display: grid;
      grid-template-columns: repeat(4, minmax(0, 1fr));
      gap: 10px;
    }

    .mini-stat {
      padding: 12px;
      border-radius: 16px;
      background: #f8fbff;
      border: 1px solid var(--line);
    }

    .mini-stat .k {
      font-size: 12px;
      color: var(--sub);
      font-weight: 700;
      margin-bottom: 6px;
    }

    .mini-stat .v {
      font-size: 20px;
      font-weight: 800;
    }

    .summary-grid {
      grid-template-columns: 1.2fr 1fr 1fr;
    }

    .summary-card ul {
      margin: 10px 0 0;
      padding-left: 18px;
      color: var(--sub);
      line-height: 1.75;
      font-size: 14px;
    }

    .chart-card,
    .table-card {
      padding: 20px;
      margin-top: 18px;
    }

    .chart-canvas {
      width: 100%;
      height: 340px;
      display: block;
      margin-top: 14px;
      background: linear-gradient(180deg, #ffffff 0%, #fcfdff 100%);
      border-radius: 18px;
      border: 1px solid #ccd3df;
      box-shadow: inset 0 1px 0 rgba(255,255,255,0.95);
    }

    .chart-canvas.small { height: 300px; }

    .chart-2col {
      grid-template-columns: repeat(2, minmax(0, 1fr));
    }

    .table-wrap {
      margin-top: 14px;
      overflow: auto;
      border: 1px solid var(--line);
      border-radius: 18px;
    }

    table {
      width: 100%;
      border-collapse: collapse;
      min-width: 760px;
      background: #fff;
    }

    thead th {
      position: sticky;
      top: 0;
      z-index: 2;
      background: #f7faff;
      color: var(--ink);
      font-size: 16px;
      text-align: center;
      padding: 12px 10px;
      border-bottom: 1px solid var(--line);
    }

    tbody td {
      text-align: center;
      padding: 10px 8px;
      font-size: 16px;
      border-top: 1px solid #eef2f8;
      color: var(--ink);
    }

    tbody tr:nth-child(even) td { background: #fcfdff; }

    .message {
      position: fixed;
      right: 18px;
      bottom: 18px;
      background: rgba(31, 42, 68, 0.92);
      color: #fff;
      padding: 12px 16px;
      border-radius: 14px;
      box-shadow: 0 12px 26px rgba(31,42,68,0.22);
      font-size: 14px;
      opacity: 0;
      transform: translateY(14px);
      pointer-events: none;
      transition: 0.25s ease;
      max-width: 360px;
      line-height: 1.6;
    }

    .message.show {
      opacity: 1;
      transform: translateY(0);
    }

    .footnote {
      margin-top: 16px;
      text-align: center;
      font-size: 13px;
      color: var(--sub);
    }

    .reference-info {
      margin-top: 18px;
      padding: 20px;
    }

    .reference-info summary {
      cursor: pointer;
      list-style: none;
      font-size: 20px;
      font-weight: 800;
      color: var(--ink);
      user-select: none;
      display: flex;
      align-items: center;
      gap: 8px;
    }

    .reference-info summary::-webkit-details-marker {
      display: none;
    }

    .reference-info summary::before {
      content: "▶";
      font-size: 12px;
      color: var(--sub);
      transform: translateY(1px);
      transition: transform 0.2s ease;
    }

    .reference-info[open] summary::before {
      transform: rotate(90deg) translateX(1px);
    }

    .reference-info h3 {
      margin: 0;
      font-size: 20px;
    }

    .reference-info .status-strip,
    .reference-info .concept-grid {
      margin-top: 14px;
    }

    .reference-info .summary-grid {
      margin-top: 14px;
    }

    @media (max-width: 1180px) {
      .concept-grid,
      .sim-grid,
      .summary-grid,
      .chart-2col,
      .status-strip {
        grid-template-columns: repeat(2, minmax(0, 1fr));
      }
    }

    @media (max-width: 760px) {
      .concept-grid,
      .sim-grid,
      .summary-grid,
      .chart-2col,
      .status-strip,
      .stats-grid,
      .current-wrap {
        grid-template-columns: 1fr;
      }

      .app { padding: 16px 12px 34px; }
      .panel { min-height: auto; }
      .bag-grid { grid-template-columns: repeat(20, 1fr); }
      .controls-line { align-items: stretch; }
      .control-group { flex-wrap: wrap; }
      .field.inline { min-width: 100%; justify-content: space-between; }
      .field.inline input,
      .field.inline select { width: 56%; }
    }