:root {
      color-scheme: light;
      --bg: #f7f7f4;
      --ink: #18201f;
      --muted: #65716f;
      --line: #d7ddda;
      --panel: #ffffff;
      --soft: #eef4f1;
      --accent: #006d77;
      --accent-ink: #ffffff;
      --warn: #a54d00;
      --bad: #a32929;
      --good: #216e46;
      --code: #0f1716;
      --shadow: 0 10px 30px rgba(24, 32, 31, 0.08);
    }

    * {
      box-sizing: border-box;
    }

    body {
      margin: 0;
      min-height: 100vh;
      background: var(--bg);
      color: var(--ink);
      font: 14px/1.45 Inter, "Microsoft YaHei", "PingFang SC", system-ui, sans-serif;
      padding-bottom: 28px;
    }

    header {
      border-bottom: 1px solid var(--line);
      background: rgba(255, 255, 255, 0.92);
      position: sticky;
      top: 0;
      z-index: 5;
      backdrop-filter: blur(8px);
    }

    .topbar {
      max-width: 1440px;
      margin: 0 auto;
      min-height: 64px;
      padding: 12px 20px;
      display: grid;
      grid-template-columns: minmax(260px, 1fr) auto;
      gap: 16px;
      align-items: center;
    }

    h1 {
      margin: 0;
      font-size: 21px;
      line-height: 1.2;
      font-weight: 760;
      letter-spacing: 0;
    }

    .subtitle {
      color: var(--muted);
      font-size: 12px;
      margin-top: 3px;
    }

    .actions {
      display: flex;
      flex-wrap: wrap;
      gap: 8px;
      justify-content: flex-end;
    }

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

    button {
      border: 1px solid var(--line);
      background: #fff;
      color: var(--ink);
      border-radius: 7px;
      min-height: 36px;
      padding: 0 12px;
      cursor: pointer;
      transition: background 120ms ease, border-color 120ms ease, transform 120ms ease;
      white-space: nowrap;
    }

    button:hover {
      border-color: #9aa9a5;
      background: #f9fbfa;
    }

    button:active {
      transform: translateY(1px);
    }

    .primary {
      background: var(--accent);
      border-color: var(--accent);
      color: var(--accent-ink);
    }

    .primary:hover {
      background: #005d66;
      border-color: #005d66;
    }

    main {
      max-width: 1440px;
      margin: 0 auto;
      padding: 18px 20px 28px;
      display: grid;
      grid-template-columns: minmax(330px, 430px) minmax(0, 1fr);
      gap: 16px;
      align-items: start;
    }

    .panel {
      background: var(--panel);
      border: 1px solid var(--line);
      border-radius: 8px;
      box-shadow: var(--shadow);
      min-width: 0;
    }

    .panel-head {
      padding: 14px 16px 10px;
      border-bottom: 1px solid var(--line);
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 12px;
    }

    .panel-head h2 {
      margin: 0;
      font-size: 15px;
      line-height: 1.2;
      letter-spacing: 0;
    }

    .panel-body {
      padding: 14px 16px 16px;
    }

    .form-grid {
      display: grid;
      gap: 12px;
    }

    .input-file-actions {
      display: flex;
      gap: 8px;
      flex-wrap: wrap;
      justify-content: flex-start;
    }

    .input-file-actions button {
      min-height: 30px;
      padding: 0 10px;
      font-size: 12px;
    }

    label {
      display: grid;
      gap: 6px;
      color: var(--ink);
      font-weight: 650;
      min-width: 0;
    }

    .label-row {
      display: flex;
      justify-content: space-between;
      gap: 10px;
      align-items: baseline;
    }

    .hint {
      color: var(--muted);
      font-size: 12px;
      font-weight: 500;
    }

    textarea, input[type="text"], input[type="number"], select {
      width: 100%;
      border: 1px solid var(--line);
      border-radius: 7px;
      background: #fbfcfb;
      color: var(--ink);
      padding: 9px 10px;
      outline: none;
      min-width: 0;
    }

    textarea {
      resize: vertical;
      min-height: 96px;
      font-family: "Cascadia Mono", Consolas, monospace;
      line-height: 1.42;
      tab-size: 2;
    }

    textarea:focus, input:focus {
      border-color: var(--accent);
      box-shadow: 0 0 0 3px rgba(0, 109, 119, 0.12);
    }

    .fixed-field {
      border: 1px solid var(--line);
      border-radius: 7px;
      background: #f3f6f4;
      color: var(--ink);
      padding: 9px 10px;
      min-height: 38px;
      font-weight: 650;
    }

    .two {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 10px;
    }

    .three {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 10px;
    }

    .advanced-options {
      border: 1px solid var(--line);
      border-radius: 8px;
      background: #fbfcfb;
      overflow: hidden;
    }

    .advanced-options summary {
      min-height: 36px;
      padding: 8px 10px;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 10px;
      font-weight: 760;
      list-style: none;
    }

    .advanced-options summary::-webkit-details-marker {
      display: none;
    }

    .advanced-options summary::before {
      content: "+";
      display: inline-grid;
      place-items: center;
      width: 18px;
      height: 18px;
      border: 1px solid var(--line);
      border-radius: 5px;
      color: var(--accent);
      background: #fff;
      margin-right: 2px;
      flex: 0 0 auto;
    }

    .advanced-options[open] summary {
      border-bottom: 1px solid var(--line);
    }

    .advanced-options[open] summary::before {
      content: "-";
    }

    .advanced-options .advanced-title {
      flex: 1;
    }

    .advanced-grid {
      padding: 10px;
      display: grid;
      grid-template-columns: repeat(2, minmax(0, 1fr));
      gap: 10px;
    }

    .switch-row {
      display: flex;
      align-items: center;
      gap: 8px;
      min-height: 34px;
      color: var(--ink);
      font-weight: 650;
    }

    .switch-row input {
      width: 18px;
      height: 18px;
      accent-color: var(--accent);
    }

    .mode-switch {
      display: grid;
      gap: 7px;
    }

    .segmented {
      display: inline-flex;
      width: fit-content;
      gap: 4px;
      padding: 4px;
      border: 1px solid var(--line);
      border-radius: 8px;
      background: #f6f8f7;
    }

    .mode-btn {
      min-height: 30px;
      border-color: transparent;
      background: transparent;
      padding: 0 10px;
    }

    .mode-btn.active {
      background: var(--accent);
      color: #fff;
      border-color: var(--accent);
    }

    .quiver-input[hidden] {
      display: none;
    }

    .draw-editor {
      display: grid;
      gap: 8px;
    }

    .draw-canvas {
      display: block;
      width: 100%;
      height: 260px;
      border: 1px solid var(--line);
      border-radius: 8px;
      background: #fbfcfb;
      touch-action: none;
      user-select: none;
    }

    .draw-background {
      fill: #fbfcfb;
    }

    .draw-edge {
      fill: none;
      stroke: var(--accent);
      stroke-width: 1.8;
      marker-end: url(#drawArrowMarker);
    }

    .draw-edge-label {
      fill: #273532;
      font-size: 12px;
      font-weight: 650;
      pointer-events: none;
    }

    .draw-node {
      cursor: grab;
    }

    .draw-node:active {
      cursor: grabbing;
    }

    .draw-node circle {
      fill: #ffffff;
      stroke: #9fb0ac;
      stroke-width: 1.5;
    }

    .draw-node text {
      fill: var(--ink);
      font-size: 13px;
      font-weight: 700;
      pointer-events: none;
    }

    .draw-node.selected circle {
      stroke: var(--accent);
      stroke-width: 2.5;
      filter: drop-shadow(0 3px 8px rgba(0, 109, 119, 0.18));
    }

    .draw-actions {
      display: flex;
      gap: 8px;
      justify-content: flex-end;
    }

    .tabs {
      display: flex;
      gap: 6px;
      flex-wrap: wrap;
    }

    .tab {
      min-height: 32px;
      padding: 0 10px;
      background: var(--soft);
      border-color: transparent;
      color: #273532;
    }

    .tab.active {
      background: var(--accent);
      color: #fff;
      border-color: var(--accent);
    }

    .status {
      display: flex;
      flex-wrap: wrap;
      gap: 8px;
      margin-bottom: 12px;
    }

    .pill {
      display: inline-flex;
      align-items: center;
      min-height: 26px;
      padding: 0 9px;
      border-radius: 999px;
      border: 1px solid var(--line);
      background: #fff;
      color: var(--muted);
      font-size: 12px;
      white-space: nowrap;
    }

    .pill.good {
      color: var(--good);
      border-color: rgba(33, 110, 70, 0.22);
      background: #eff8f2;
    }

    .pill.warn {
      color: var(--warn);
      border-color: rgba(165, 77, 0, 0.22);
      background: #fff7ed;
    }

    .pill.bad {
      color: var(--bad);
      border-color: rgba(163, 41, 41, 0.22);
      background: #fff0f0;
    }

    .section {
      display: none;
    }

    .section.active {
      display: block;
    }

    .output-grid {
      display: grid;
      gap: 12px;
    }

    .basic-combo {
      display: grid;
      grid-template-columns: minmax(0, 2fr) minmax(220px, 1fr);
      gap: 0;
    }

    .basic-combo > div + div {
      border-left: 1px solid var(--line);
    }

    .subhead {
      padding: 9px 12px 0;
      color: var(--muted);
      font-size: 12px;
      font-weight: 750;
    }

    .result-block {
      border: 1px solid var(--line);
      border-radius: 8px;
      overflow: hidden;
      background: #fff;
    }

    .result-title {
      min-height: 38px;
      padding: 9px 11px;
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 10px;
      background: #f3f6f4;
      border-bottom: 1px solid var(--line);
      font-weight: 760;
    }

    .result-title small {
      color: var(--muted);
      font-weight: 550;
    }

    ol, ul {
      margin: 0;
      padding: 10px 12px 12px 30px;
    }

    li {
      margin: 6px 0;
      overflow-wrap: anywhere;
    }

    code, pre {
      font-family: "Cascadia Mono", Consolas, monospace;
    }

    code {
      background: #eef4f1;
      border-radius: 5px;
      padding: 1px 4px;
    }

    pre {
      margin: 0;
      padding: 12px;
      white-space: pre-wrap;
      overflow-wrap: anywhere;
      color: var(--code);
      background: #fbfcfb;
      max-height: 520px;
      overflow: auto;
    }

    .empty {
      padding: 18px 12px;
      color: var(--muted);
    }

    .chain-list {
      max-height: 560px;
      overflow: auto;
    }

    .chain-pick {
      width: 100%;
      height: auto;
      min-height: 32px;
      justify-content: flex-start;
      text-align: left;
      white-space: normal;
      line-height: 1.4;
      padding: 6px 8px;
    }

    .zigzag-paths {
      max-height: 560px;
      overflow: auto;
    }

    .zigzag-paths li {
      margin-bottom: 10px;
    }

    .zigzag-kind {
      font-weight: 760;
    }

    .zigzag-kind.thick {
      color: #1d4ed8;
    }

    .zigzag-kind.dotted {
      color: #b91c1c;
    }

    .math-detail {
      padding: 12px;
      background: #fbfcfb;
      color: var(--ink);
      max-height: 560px;
      overflow: auto;
    }

    .math-section {
      margin-bottom: 16px;
    }

    .math-section:last-child {
      margin-bottom: 0;
    }

    .math-heading {
      font-weight: 760;
      margin-bottom: 8px;
    }

    .math-list {
      display: grid;
      gap: 6px;
      margin: 0;
      padding: 0;
      list-style: none;
    }

    .math-list li {
      margin: 0;
      padding: 7px 8px;
      border: 1px solid var(--line);
      border-radius: 7px;
      background: #ffffff;
    }

    .math {
      font-family: Georgia, "Times New Roman", "Cambria Math", serif;
      font-size: 15px;
      line-height: 1.45;
      overflow-wrap: anywhere;
    }

    .math-index {
      color: var(--muted);
      font-size: 12px;
      margin-right: 4px;
    }

    .math-tensor {
      display: inline-block;
      margin: 0 2px;
      white-space: nowrap;
    }

    .math-frac sup,
    .math-frac sub,
    .math-tensor sup,
    .math-tensor sub {
      line-height: 0;
      font-size: 0.72em;
    }

    .math-log {
      padding: 12px;
      background: #fbfcfb;
      color: var(--ink);
      display: grid;
      gap: 8px;
    }

    .math-muted {
      color: var(--muted);
      font-size: 13px;
    }

    .diagram-canvas {
      overflow: auto;
      background: #fbfcfb;
      border-bottom: 1px solid var(--line);
      min-height: 260px;
    }

    .diagram-canvas svg {
      display: block;
      min-width: 100%;
      touch-action: none;
      user-select: none;
    }

    .diagram-node {
      cursor: grab;
    }

    .diagram-node.dragging {
      cursor: grabbing;
    }

    .diagram-node rect {
      transition: stroke 120ms ease, filter 120ms ease;
    }

    .diagram-node:hover rect,
    .diagram-node.dragging rect {
      stroke: var(--accent);
      filter: drop-shadow(0 3px 8px rgba(0, 109, 119, 0.16));
    }

    .diagram-edge-label {
      pointer-events: none;
    }

    .tikz-code {
      max-height: 340px;
      overflow: auto;
    }

    .copy-btn {
      min-height: 28px;
      padding: 0 8px;
      font-size: 12px;
    }

    .references {
      padding: 12px;
      display: grid;
      gap: 8px;
      line-height: 1.45;
      color: var(--ink);
      background: #fbfcfb;
    }

    .references p {
      margin: 0;
      overflow-wrap: anywhere;
    }

    .reference-heading {
      margin-top: 4px;
      font-weight: 760;
    }

    .reference-heading:first-child {
      margin-top: 0;
    }

    .contact-note {
      position: fixed;
      right: 12px;
      bottom: 8px;
      z-index: 8;
      color: var(--muted);
      font-size: 11px;
      line-height: 1.25;
      background: rgba(255, 255, 255, 0.86);
      border: 1px solid rgba(215, 221, 218, 0.8);
      border-radius: 6px;
      padding: 4px 7px;
      box-shadow: 0 4px 12px rgba(24, 32, 31, 0.06);
    }

    .contact-note a {
      color: var(--accent);
      text-decoration: none;
    }

    .contact-note a:hover {
      text-decoration: underline;
    }

    .metric-table {
      width: 100%;
      border-collapse: collapse;
      font-size: 13px;
    }

    .metric-table th,
    .metric-table td {
      text-align: left;
      padding: 8px 10px;
      border-bottom: 1px solid var(--line);
      vertical-align: top;
      overflow-wrap: anywhere;
    }

    .metric-table th {
      width: 170px;
      color: var(--muted);
      font-weight: 650;
      background: #fbfcfb;
    }

    .error-box {
      border: 1px solid rgba(163, 41, 41, 0.26);
      background: #fff4f4;
      color: var(--bad);
      padding: 11px 12px;
      border-radius: 8px;
      white-space: pre-wrap;
    }

    @media (max-width: 980px) {
      .topbar,
      main {
        grid-template-columns: 1fr;
      }

      .actions {
        justify-content: flex-start;
      }
    }

    @media (max-width: 620px) {
      .topbar,
      main {
        padding-left: 12px;
        padding-right: 12px;
      }

      .two,
      .three,
      .advanced-grid,
      .basic-combo {
        grid-template-columns: 1fr;
      }

      .basic-combo > div + div {
        border-left: 0;
        border-top: 1px solid var(--line);
      }

      h1 {
        font-size: 18px;
      }
    }