:root {
      --bg: #f3f5f8;
      --panel: #ffffff;
      --border: #d6dce5;
      --text: #20242a;
      --muted: #667085;
      --primary: #155eef;
      --primary-hover: #004ee0;
      --success: #217346;
      --danger: #b42318;
      --warning: #9a6700;
      --soft: #f8fafc;
    }

    * {
      box-sizing: border-box;
    }

    body {
      margin: 0;
      padding: 14px;
      background: var(--bg);
      color: var(--text);
      font-family: Arial, Helvetica, sans-serif;
    }

    .app {
      max-width: 1500px;
      margin: 0 auto;
    }

    .header {
      margin-bottom: 12px;
      padding: 14px 16px;
      border: 1px solid var(--border);
      border-radius: 10px;
      background: var(--panel);
    }

    .header h1 {
      margin: 0;
      font-size: 20px;
    }

    .header p {
      margin: 6px 0 0;
      color: var(--muted);
      font-size: 13px;
      line-height: 1.45;
    }

    .layout {
      display: grid;
      grid-template-columns: 360px minmax(0, 1fr);
      gap: 12px;
    }

    .panel {
      border: 1px solid var(--border);
      border-radius: 10px;
      background: var(--panel);
    }

    .controls {
      padding: 14px;
      align-self: start;
    }

    .controls h2 {
      margin: 0 0 12px;
      font-size: 16px;
    }

    .form-row {
      margin-bottom: 10px;
    }

    .form-row label {
      display: block;
      margin-bottom: 5px;
      font-size: 12px;
      font-weight: bold;
    }

    input,
    select,
    button {
      font: inherit;
    }

    input[type="text"],
    input[type="number"],
    select {
      width: 100%;
      padding: 8px 9px;
      border: 1px solid #aeb7c2;
      border-radius: 6px;
      background: white;
      font-size: 13px;
    }

    button {
      padding: 9px 13px;
      border: 1px solid #8c96a3;
      border-radius: 6px;
      background: white;
      cursor: pointer;
      font-size: 13px;
    }

    button:hover {
      background: #f2f4f7;
    }

    button.primary {
      border-color: var(--primary);
      background: var(--primary);
      color: white;
      font-weight: bold;
    }

    button.primary:hover {
      background: var(--primary-hover);
    }

    button.success {
      border-color: var(--success);
      background: var(--success);
      color: white;
      font-weight: bold;
    }

    button.success:hover {
      filter: brightness(0.94);
    }

    button:disabled,
    select:disabled,
    input:disabled {
      cursor: not-allowed;
      opacity: 0.55;
    }

    .two-col {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 8px;
    }

    .button-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 8px;
      margin-top: 12px;
    }

    .button-grid .wide {
      grid-column: 1 / -1;
    }

    .group {
      margin: 12px 0;
      padding: 10px;
      border: 1px solid var(--border);
      border-radius: 7px;
      background: #fbfcfd;
    }

    .group-title {
      margin-bottom: 9px;
      font-size: 12px;
      font-weight: bold;
    }

    .status {
      min-height: 24px;
      margin-top: 10px;
      font-size: 12px;
      line-height: 1.45;
      color: var(--muted);
    }

    .status.success {
      color: var(--success);
    }

    .status.error {
      color: var(--danger);
    }

    .status.warning {
      color: var(--warning);
    }

    .summary-wrap {
      max-height: 355px;
      margin-top: 12px;
      overflow: auto;
      border: 1px solid var(--border);
      border-radius: 7px;
    }

    table {
      width: 100%;
      border-collapse: collapse;
      font-size: 11px;
    }

    th,
    td {
      padding: 7px 8px;
      border-bottom: 1px solid var(--border);
      text-align: right;
      white-space: nowrap;
    }

    th:first-child,
    td:first-child {
      text-align: center;
    }

    th {
      position: sticky;
      top: 0;
      z-index: 2;
      background: #eef2f7;
    }

    .workspace {
      min-width: 0;
      overflow: hidden;
    }

    .tabs {
      display: flex;
      gap: 4px;
      padding: 8px 8px 0;
      border-bottom: 1px solid var(--border);
      background: #eef2f7;
    }

    .tab-button {
      padding: 10px 16px;
      border: 1px solid transparent;
      border-bottom: none;
      border-radius: 7px 7px 0 0;
      background: transparent;
      font-weight: bold;
    }

    .tab-button.active {
      border-color: var(--border);
      background: white;
    }

    .tab-content {
      display: none;
      padding: 14px;
    }

    .tab-content.active {
      display: block;
    }

    .main-card {
      min-height: 600px;
      padding: 24px;
      border: 1px solid var(--border);
      border-radius: 8px;
      background: white;
    }

    .main-card h2 {
      margin-top: 0;
    }

    .main-card p {
      max-width: 780px;
      color: var(--muted);
      line-height: 1.65;
    }

    .formula {
      margin: 20px 0;
      padding: 14px;
      border: 1px solid var(--border);
      border-radius: 7px;
      background: var(--soft);
      font-family: "Times New Roman", serif;
      font-size: 17px;
      line-height: 1.7;
    }

    .copyright {
      margin-top: 300px;
      color: var(--muted);
      text-align: right;
      font-size: 12px;
    }

    .chart-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 12px;
    }

    .chart-panel {
      min-width: 0;
    }

    .chart-panel.full {
      grid-column: 1 / -1;
    }

    .chart-title {
      margin-bottom: 6px;
      font-size: 13px;
      font-weight: bold;
    }

    .chart-wrap {
      position: relative;
      min-height: 330px;
      padding: 7px;
      border: 1px solid var(--border);
      border-radius: 7px;
      background: white;
    }

    .animation-controls {
      display: grid;
      grid-template-columns:
        minmax(180px, 1fr)
        auto auto auto
        minmax(150px, 220px)
        auto;
      gap: 8px;
      align-items: center;
      margin-bottom: 10px;
    }

    .speed-box {
      display: grid;
      grid-template-columns: auto 1fr auto;
      gap: 7px;
      align-items: center;
      font-size: 12px;
    }

    .animation-grid {
      display: grid;
      grid-template-rows: minmax(430px, 1fr) 270px;
      gap: 12px;
    }

    .canvas-wrap {
      padding: 7px;
      border: 1px solid var(--border);
      border-radius: 7px;
      background: white;
    }

    #sceneCanvas {
      display: block;
      width: 100%;
      height: 430px;
    }

    .anim-info {
      min-width: 115px;
      color: var(--muted);
      font-size: 12px;
      text-align: right;
    }

    .note {
      margin-top: 10px;
      color: var(--muted);
      font-size: 11px;
      line-height: 1.45;
    }

    @media (max-width: 1120px) {
      .layout {
        grid-template-columns: 1fr;
      }

      .animation-controls {
        grid-template-columns: 1fr 1fr 1fr;
      }

      .speed-box {
        grid-column: span 2;
      }
    }

    @media (max-width: 720px) {
      body {
        padding: 8px;
      }

      .two-col,
      .button-grid,
      .chart-grid,
      .animation-controls {
        grid-template-columns: 1fr;
      }

      .button-grid .wide,
      .chart-panel.full,
      .speed-box {
        grid-column: auto;
      }

      #sceneCanvas {
        height: 340px;
      }
    }

.backend-status {
  display: inline-block;
  margin-top: 8px;
  padding: 5px 9px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--soft);
  color: var(--muted);
  font-size: 12px;
  font-weight: bold;
}

.backend-status.online {
  border-color: #86efac;
  background: #f0fdf4;
  color: var(--success);
}

.backend-status.offline {
  border-color: #fca5a5;
  background: #fef2f2;
  color: var(--danger);
}