:root {
      color-scheme: light;
      --bg: #f6f7fb;
      --panel: #ffffff;
      --panel-muted: #f8f9fc;
      --text: #101828;
      --muted: #475467;
      --line: #d0d5dd;
      --line-strong: #98a2b3;
      --accent: #2563eb;
      --accent-soft: #dbeafe;
      --success: #0f766e;
      --success-soft: #ccfbf1;
      --warn: #b45309;
      --warn-soft: #fef3c7;
      --danger: #b42318;
      --danger-soft: #fee4e2;
      --shadow: 0 18px 40px rgba(16, 24, 40, 0.08);
      --radius-lg: 18px;
      --radius-md: 12px;
      --radius-sm: 10px;
      --app-shell-max: 1320px;
      --rail-divider-color: rgba(15, 23, 42, 0.12);
      --mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
      --sans: Inter, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    }

    

    * {
      box-sizing: border-box;
    }

    html,
    body {
      margin: 0;
      padding: 0;
      background: linear-gradient(180deg, var(--bg), color-mix(in srgb, var(--bg) 82%, var(--panel) 18%));
      color: var(--text);
      font-family: var(--sans);
    }

    body {
      min-height: 100vh;
      line-height: 1.5;
    }

    button,
    select,
    input,
    textarea {
      font: inherit;
      color: inherit;
    }

    button {
      cursor: pointer;
      border: 1px solid var(--line);
      background: var(--panel);
      border-radius: 10px;
      min-height: 42px;
      padding: 10px 14px;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      transition: transform 140ms ease, border-color 140ms ease, background 140ms ease, opacity 140ms ease;
    }

    button:hover:not(:disabled) {
      border-color: var(--line-strong);
      transform: translateY(-1px);
    }

    button:disabled {
      opacity: 0.55;
      cursor: not-allowed;
      transform: none;
    }

    .equation-shell {
      width: min(1440px, calc(100vw - 32px));
      margin: 24px auto 48px;
      display: grid;
      gap: 18px;
    }

    .equation-hero-panel {
      background: radial-gradient(circle at top left, color-mix(in srgb, var(--accent) 10%, var(--panel) 90%), var(--panel));
      border: 1px solid var(--line);
      border-radius: 22px;
      padding: 22px 24px;
      box-shadow: var(--shadow);
      display: grid;
      gap: 10px;
    }

    h1 {
      margin: 0;
      font-size: clamp(1.5rem, 2vw + 1rem, 2.3rem);
      line-height: 1.2;
    }

    .subtitle {
      margin: 0;
      color: var(--muted);
      max-width: 74ch;
    }

    .layout {
      display: grid;
      grid-template-columns: minmax(420px, 1.2fr) minmax(320px, 0.9fr);
      gap: 18px;
      align-items: stretch;
      margin: 1rem auto 0;
    }

    .panel-stack {
      display: grid;
      gap: 18px;
      min-width: 0;
      align-content: start;
    }

    .panel-stack--output {
      height: 100%;
      align-content: stretch;
    }

    .panel {
      background: var(--panel);
      border: 1px solid var(--line);
      border-radius: var(--radius-lg);
      box-shadow: var(--shadow);
      padding: 18px;
      display: grid;
      gap: 14px;
      min-width: 0;
    }

    .panel h2,
    .panel h3,
    .panel h4 {
      margin: 0;
      line-height: 1.2;
    }

    .panel-head,
    .editor-footer,
    .preview-head,
    .output-head {
      display: flex;
      justify-content: space-between;
      align-items: flex-start;
      gap: 12px;
      flex-wrap: wrap;
    }

    .builder-card-head {
      display: flex;
      justify-content: space-between;
      align-items: center;
      gap: 12px;
      flex-wrap: wrap;
    }

    .section-intro {
      margin: 4px 0 0;
      color: var(--muted);
      font-size: 0.96rem;
    }

    .cluster,
    .row,
    .control-row,
    .button-row {
      display: flex;
      flex-wrap: wrap;
      gap: 12px;
      align-items: stretch;
      min-width: 0;
    }

    .control-row > *,
    .row > * {
      flex: 1 1 180px;
      min-width: 0;
    }

    .field,
    .builder-field,
    .editor-pane,
    .preview-pane {
      display: grid;
      gap: 8px;
      min-width: 0;
      align-content: start;
    }

    .builder-field--full {
      grid-column: 1 / -1;
    }

    .field label,
    .builder-field label,
    .inline-label {
      font-size: 0.92rem;
      color: var(--muted);
    }

    .field input,
    .field select,
    .builder-field input,
    .builder-field select,
    .builder-field textarea,
    textarea,
    .output-box {
      width: 100%;
      border: 1px solid var(--line);
      border-radius: var(--radius-md);
      background: var(--panel-muted);
      padding: 12px 14px;
    }

    textarea,
    .output-box {
      font-family: var(--mono);
      font-size: 0.94rem;
      line-height: 1.55;
      resize: vertical;
      tab-size: 2;
    }

    .workspace-grid {
      display: grid;
      gap: 16px;
      grid-template-columns: minmax(320px, 1.15fr) minmax(260px, 0.85fr);
      align-items: start;
    }

    .editor {
      min-height: 290px;
    }

    .mini-textarea {
      min-height: 94px;
    }

    .meta-stack {
      display: grid;
      gap: 4px;
    }

    .editor-meta,
    .output-meta,
    .preview-status-text {
      font-size: 0.88rem;
      color: var(--muted);
    }

    .preview-shell {
      display: grid;
      gap: 10px;
    }

    .preview-board {
      min-height: 220px;
      border: 1px dashed var(--line-strong);
      border-radius: var(--radius-md);
      background: linear-gradient(180deg, color-mix(in srgb, var(--panel-muted) 90%, transparent 10%), var(--panel));
      padding: 18px;
      overflow-x: auto;
      overflow-y: visible;
    }

    .placeholder {
      color: var(--muted);
      display: grid;
      place-items: center;
      min-height: 150px;
      text-align: center;
      padding: 22px;
      border-radius: var(--radius-md);
      background: color-mix(in srgb, var(--panel-muted) 90%, transparent 10%);
    }

    .status-badge {
      display: inline-flex;
      align-items: center;
      gap: 8px;
      padding: 8px 11px;
      border-radius: 999px;
      border: 1px solid var(--line);
      background: var(--panel-muted);
      font-size: 0.88rem;
      white-space: nowrap;
    }

    .status-badge[data-tone="ready"] {
      background: var(--success-soft);
      border-color: color-mix(in srgb, var(--success) 40%, var(--line) 60%);
      color: color-mix(in srgb, var(--success) 82%, black 18%);
    }

    .status-badge[data-tone="loading"] {
      background: var(--accent-soft);
      border-color: color-mix(in srgb, var(--accent) 36%, var(--line) 64%);
      color: color-mix(in srgb, var(--accent) 82%, black 18%);
    }

    .status-badge[data-tone="warn"] {
      background: var(--warn-soft);
      border-color: color-mix(in srgb, var(--warn) 40%, var(--line) 60%);
      color: color-mix(in srgb, var(--warn) 90%, black 10%);
    }

    .status-badge[data-tone="error"] {
      background: var(--danger-soft);
      border-color: color-mix(in srgb, var(--danger) 40%, var(--line) 60%);
      color: color-mix(in srgb, var(--danger) 90%, black 10%);
    }

    .primary-btn {
      background: var(--accent);
      color: white;
      border-color: color-mix(in srgb, var(--accent) 70%, black 30%);
    }

    .secondary-btn {
      background: var(--panel-muted);
    }

    .ghost-btn {
      background: transparent;
    }

    .tiny-btn {
      padding: 8px 10px;
      font-size: 0.88rem;
    }

    .full-btn {
      width: 100%;
      padding: 11px 12px;
    }

    .tab-shell {
      display: grid;
      gap: 14px;
    }

    .tab-list {
      display: flex;
      gap: 8px;
      flex-wrap: wrap;
      padding: 6px;
      border: 1px solid var(--line);
      border-radius: calc(var(--radius-md) + 2px);
      background: color-mix(in srgb, var(--panel-muted) 64%, transparent 36%);
    }

    .tab-btn {
      flex: 1 1 160px;
      padding: 10px 14px;
      border-radius: 10px;
      border: 1px solid transparent;
      background: transparent;
      color: var(--muted);
      font-weight: 600;
      text-align: center;
    }

    .tab-btn:hover {
      background: color-mix(in srgb, var(--panel) 65%, transparent 35%);
    }

    .tab-btn[aria-selected="true"] {
      background: var(--panel);
      border-color: var(--line);
      color: var(--text);
      box-shadow: 0 1px 0 color-mix(in srgb, var(--panel) 90%, transparent 10%);
    }

    .tab-panel {
      border: 1px solid var(--line);
      border-radius: var(--radius-md);
      background: color-mix(in srgb, var(--panel-muted) 52%, transparent 48%);
      padding: 16px;
      display: grid;
      gap: 16px;
    }

    .tab-panel[hidden] {
      display: none;
    }

    .symbol-grid {
      display: grid;
      gap: 8px;
      grid-template-columns: repeat(auto-fit, minmax(102px, 1fr));
    }

    .snippet-grid {
      display: grid;
      gap: 8px;
      grid-template-columns: repeat(auto-fit, minmax(142px, 1fr));
    }

    .symbol-btn,
    .snippet-btn {
      min-width: 0;
      min-height: 74px;
      padding: 12px;
      display: grid;
      gap: 6px;
      justify-items: center;
      align-content: center;
      text-align: center;
      overflow: hidden;
    }

    .symbol-btn .btn-label,
    .snippet-btn .btn-label {
      font-weight: 600;
      line-height: 1.25;
    }

    .symbol-btn .btn-code,
    .snippet-btn .btn-code {
      display: block;
      width: 100%;
      font-family: var(--mono);
      font-size: 0.82rem;
      color: var(--muted);
      line-height: 1.35;
      white-space: normal;
      overflow-wrap: anywhere;
      word-break: break-word;
      text-align: center;
    }

    .builder-grid {
      display: grid;
      gap: 12px;
      grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    }

    .builder-grid.tight {
      grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
    }

    .builder-card {
      border: 1px solid var(--line);
      background: color-mix(in srgb, var(--panel-muted) 70%, transparent 30%);
      border-radius: var(--radius-md);
      padding: 14px;
      display: grid;
      gap: 12px;
      align-content: start;
    }

    .builder-preview-shell {
      display: grid;
      gap: 8px;
      padding: 10px 12px;
      border: 1px solid color-mix(in srgb, var(--accent) 18%, var(--line) 82%);
      border-radius: var(--radius-md);
      background: linear-gradient(
        180deg,
        color-mix(in srgb, var(--accent-soft) 36%, var(--panel) 64%),
        color-mix(in srgb, var(--panel-muted) 72%, transparent 28%)
      );
    }

    .builder-preview-label {
      margin: 0;
      color: var(--muted);
      font-size: 0.78rem;
      font-weight: 700;
      letter-spacing: 0.03em;
      text-transform: uppercase;
    }

    .builder-preview-canvas {
      min-height: 84px;
      border: 1px dashed color-mix(in srgb, var(--accent) 28%, var(--line) 72%);
      border-radius: var(--radius-sm);
      background: color-mix(in srgb, var(--panel) 90%, var(--accent-soft) 10%);
      padding: 10px 12px;
      display: grid;
      place-items: center;
      overflow: auto;
      text-align: center;
    }

    .builder-preview-canvas.is-fallback {
      place-items: stretch;
    }

    .builder-preview-canvas.is-fallback {
      font-family: var(--mono);
      font-size: 0.85rem;
      line-height: 1.45;
      color: var(--muted);
      white-space: pre-wrap;
      word-break: break-word;
    }

    .builder-preview-canvas mjx-container {
      margin: 0 !important;
      font-size: 105% !important;
    }

    .output-focus-card {
      border: 1px solid var(--line);
      border-radius: var(--radius-md);
      padding: 14px;
      background: color-mix(in srgb, var(--panel-muted) 56%, transparent 44%);
      display: grid;
      gap: 10px;
    }

    .output-panel {
      height: 100%;
      min-height: 100%;
      min-width: 0;
      align-content: stretch;
      grid-template-rows: auto auto auto minmax(0, 1fr) auto;
    }

    .output-panel > * {
      min-width: 0;
    }

    .output-code-card {
      min-height: 0;
      height: 100%;
      align-content: stretch;
      grid-template-rows: auto minmax(0, 1fr) auto;
    }

    .output-box {
      min-height: 320px;
      background: color-mix(in srgb, var(--panel-muted) 78%, transparent 22%);
      overflow-y: auto;
      resize: none;
      min-width: 0;
    }

    .footer-note {
      color: var(--muted);
      font-size: 0.92rem;
    }

    .mono {
      font-family: var(--mono);
    }

    .hint-box {
      border-left: 4px solid var(--accent);
      background: color-mix(in srgb, var(--accent-soft) 65%, transparent 35%);
      border-radius: 0 var(--radius-md) var(--radius-md) 0;
      padding: 12px 14px;
      color: var(--text);
      font-size: 0.92rem;
    }

    .kbd {
      font-family: var(--mono);
      font-size: 0.82rem;
      padding: 2px 6px;
      border-radius: 6px;
      border: 1px solid var(--line);
      background: var(--panel-muted);
      white-space: nowrap;
    }

    .guide-layout {
      margin: 1rem auto 0;
      display: grid;
      gap: 1rem;
      grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    }

    .guide-card {
      border: 1px solid var(--line);
      border-radius: var(--radius-lg);
      background: var(--panel);
      box-shadow: var(--shadow);
      padding: 18px;
      display: grid;
      gap: 0.85rem;
    }

    .guide-card p,
    .guide-card ol,
    .guide-card ul {
      margin: 0;
      color: var(--muted);
    }

    .guide-card ol,
    .guide-card ul {
      padding-left: 1.2rem;
    }

    .updated-at {
      color: var(--muted);
      font-size: 0.9rem;
    }

    .tool-footer {
      margin-top: 2rem;
      padding-bottom: 1rem;
    }

    .tool-footer__inner {
      padding-bottom: 1rem;
    }

    .tool-footer__nav {
      display: flex;
      flex-wrap: wrap;
      gap: 0.5rem 1rem;
      margin-bottom: 0.9rem;
    }

    .tool-footer__nav a {
      color: inherit;
      text-decoration: none;
    }

    .tool-footer__nav a:hover,
    .tool-footer__nav a:focus-visible {
      text-decoration: underline;
    }

    .tool-footer__meta,
    .tool-footer__note {
      margin: 0 0 0.7rem;
      color: var(--muted);
      line-height: 1.6;
    }

    @media (min-width: 1081px) {
      .output-panel.stick-top {
        position: sticky;
        top: 18px;
      }

      .output-panel.stick-bottom {
        position: sticky;
        bottom: 18px;
      }
    }

    @media (max-width: 1080px) {
      .layout {
        grid-template-columns: 1fr;
      }

      .output-panel {
        position: static;
        height: auto;
        min-height: 0;
        grid-template-rows: auto;
      }

      .panel-stack--output {
        height: auto;
      }
    }

    @media (max-width: 920px) {
      .workspace-grid {
        grid-template-columns: 1fr;
      }
    }

    @media (max-width: 720px) {
      .equation-shell {
        width: min(100vw - 20px, 100%);
        margin: 12px auto 28px;
      }

      .equation-hero-panel,
      .panel {
        padding: 16px;
      }

      .panel-head,
      .preview-head,
      .output-head {
        flex-direction: column;
        align-items: stretch;
      }

      .button-row {
        display: grid;
        grid-template-columns: 1fr;
      }

      .button-row > * {
        width: 100%;
      }

      .symbol-grid {
        grid-template-columns: repeat(auto-fit, minmax(92px, 1fr));
      }

      .snippet-grid {
        grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
      }

      .output-box {
        min-height: 280px;
      }
    }