/* 平面几何画板样式（第二轮）
   设计遵循：工作区 /Users/shark/Documents/Shark/设计规范.md §10 / §11。
   - 语义色 token：bg/surface/border/text/secondaryText/accent/danger/success
   - 画布专用 token：--canvas-*，浅色 / 深色各一套，供 JS 读取后绘制 JSXGraph
   - 主题三态：:root[data-theme="auto|light|dark"]，auto 跟随 prefers-color-scheme
   - 间距 4/8/12/16/20/24/32；圆角 8/12/16；动效 150–220ms
   - 触控热区 ≥ 44px；焦点环 3px outline + 2px offset
   - 对比度：浅色主色加深、深色主色单独取值，均满足正文 4.5:1 */

:root {
  color-scheme: light;
  --color-label: #000000;
  --color-secondary-label: #3c3c43;
  --color-background: #ffffff;
  --color-secondary-background: #f2f2f7;
  --color-separator: rgba(60, 60, 67, 0.29);

  --color-bg: var(--color-background);
  --color-surface: var(--color-secondary-background);
  --color-surface-raised: #ffffff;
  --color-text-primary: var(--color-label);
  --color-text-secondary: var(--color-secondary-label);
  --color-border: var(--color-separator);
  /* 控件边界：与背景 ≥3:1，避免只靠浅分隔线 */
  --color-control-border: #86868b;

  --color-primary: #0062cc;
  --color-primary-hover: #004f9f;
  --color-primary-soft: rgba(0, 122, 255, 0.14);
  --color-primary-text: #ffffff;
  --color-focus: #007aff;
  --color-error: #d70015;
  --color-error-soft: rgba(255, 59, 48, 0.10);
  --color-success: #248a3d;
  --color-success-soft: rgba(52, 199, 89, 0.25);
  --color-warn: #8a4b00;
  --color-warn-bg: rgba(255, 149, 0, 0.12);
  --color-active-bar: #ffd166;
  --color-overlay-bg: rgba(255, 255, 255, 0.94);

  --canvas-bg: #ffffff;
  --canvas-point: #1d4ed8;
  --canvas-point-stroke: #1e3a8a;
  --canvas-line: #334155;
  --canvas-circle: #0f766e;
  --canvas-ellipse: #7c3aed;
  --canvas-helper: #94a3b8;
  --canvas-aux: #64748b;
  --canvas-axis: #64748b;
  --canvas-grid: #d7dee8;
  --canvas-label: #0f172a;
  --canvas-select: #b45309;

  --radius-sm: 0.5rem;
  --radius: 0.5rem;
  --radius-md: 0.75rem;
  --radius-lg: 1rem;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.08);
  --shadow-pop: 0 8px 24px rgba(0, 0, 0, 0.16);
  --card-shadow: var(--shadow);
  --font-sans: -apple-system, BlinkMacSystemFont, "SF Pro Text", "PingFang SC", "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  /* 统一字号阶梯：12 / 13 / 14 / 15，行高按 1.25 紧凑、1.45 常规，避免中英文混排时字形压行 */
  --text-2xs: 0.75rem;
  --text-xs: 0.8125rem;
  --text-sm: 0.875rem;
  --text-md: 0.9375rem;
  --lh-tight: 1.25;
  --lh-normal: 1.45;
  /* MathLive 虚拟键盘挂在 body 上，不继承 math-field 的局部变量，必须在根上统一热区高度 */
  --keycap-height: 44px;
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --motion-quick: 150ms;
  --motion-standard: 220ms;
  --ease-standard: cubic-bezier(0.2, 0, 0, 1);
}

/* 深色：手动选择 + 跟随系统 */
:root[data-theme="dark"] {
  color-scheme: dark;
  --color-label: #f2f4f8;
  --color-secondary-label: #b7c0ce;
  --color-background: #0f1115;
  --color-secondary-background: #171a21;
  --color-surface-raised: #1e232c;
  --color-separator: rgba(255, 255, 255, 0.20);
  --color-control-border: #6b7280;

  --color-primary: #1c66e5;
  --color-primary-hover: #2a74f0;
  --color-primary-soft: rgba(92, 156, 255, 0.24);
  --color-primary-text: #ffffff;
  --color-focus: #64b5ff;
  --color-error: #ff7b72;
  --color-error-soft: rgba(255, 105, 97, 0.16);
  --color-success: #4cd964;
  --color-success-soft: rgba(76, 217, 100, 0.24);
  --color-warn: #ffb340;
  --color-warn-bg: rgba(255, 179, 64, 0.14);
  --color-active-bar: #ffd166;
  --color-overlay-bg: rgba(15, 17, 21, 0.94);

  --canvas-bg: #0f1115;
  --canvas-point: #60a5fa;
  --canvas-point-stroke: #bfdbfe;
  --canvas-line: #cbd5e1;
  --canvas-circle: #34d399;
  --canvas-ellipse: #c084fc;
  --canvas-helper: #64748b;
  --canvas-aux: #94a3b8;
  --canvas-axis: #93a4bb;
  --canvas-grid: #2b3444;
  --canvas-label: #e6ebf3;
  --canvas-select: #fbbf24;

  --shadow: 0 1px 2px rgba(0, 0, 0, 0.6);
  --shadow-pop: 0 10px 30px rgba(0, 0, 0, 0.6);
  --card-shadow: none;
}

@media (prefers-color-scheme: dark) {
  :root[data-theme="auto"] {
    color-scheme: dark;
    --color-label: #f2f4f8;
    --color-secondary-label: #b7c0ce;
    --color-background: #0f1115;
    --color-secondary-background: #171a21;
    --color-surface-raised: #1e232c;
    --color-separator: rgba(255, 255, 255, 0.20);
    --color-control-border: #6b7280;

    --color-primary: #1c66e5;
    --color-primary-hover: #2a74f0;
    --color-primary-soft: rgba(92, 156, 255, 0.24);
    --color-primary-text: #ffffff;
    --color-focus: #64b5ff;
    --color-error: #ff7b72;
    --color-error-soft: rgba(255, 105, 97, 0.16);
    --color-success: #4cd964;
    --color-success-soft: rgba(76, 217, 100, 0.24);
    --color-warn: #ffb340;
    --color-warn-bg: rgba(255, 179, 64, 0.14);
    --color-active-bar: #ffd166;
    --color-overlay-bg: rgba(15, 17, 21, 0.94);

    --canvas-bg: #0f1115;
    --canvas-point: #60a5fa;
    --canvas-point-stroke: #bfdbfe;
    --canvas-line: #cbd5e1;
    --canvas-circle: #34d399;
    --canvas-ellipse: #c084fc;
    --canvas-helper: #64748b;
    --canvas-aux: #94a3b8;
    --canvas-axis: #93a4bb;
    --canvas-grid: #2b3444;
    --canvas-label: #e6ebf3;
    --canvas-select: #fbbf24;

    --shadow: 0 1px 2px rgba(0, 0, 0, 0.6);
    --shadow-pop: 0 10px 30px rgba(0, 0, 0, 0.6);
    --card-shadow: none;
  }
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }
html, body { height: 100%; }
body {
  margin: 0;
  display: flex;
  flex-direction: column;
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.5;
  color: var(--color-text-primary);
  background: var(--color-bg);
  -webkit-tap-highlight-color: transparent;
  transition: background-color var(--motion-standard) var(--ease-standard), color var(--motion-standard) var(--ease-standard);
}

h1, h2, h3 { line-height: 1.25; margin: 0; }
h1 { font-size: 1.25rem; }
h2 { font-size: 1rem; }
h3 { font-size: 0.875rem; font-weight: 600; }
p { margin: 0; }
code { font-family: var(--font-mono); font-size: 0.8125rem; background: var(--color-surface); padding: 0 var(--space-1); border-radius: 0.25rem; }

.skip-link {
  position: absolute;
  inset-inline-start: var(--space-4);
  top: -4rem;
  z-index: 10;
  padding: var(--space-2) var(--space-4);
  background: var(--color-primary);
  color: var(--color-primary-text);
  border-radius: var(--radius);
  text-decoration: none;
}
.skip-link:focus { top: var(--space-2); }

/* ---------- 顶栏：品牌 / 工具分组 / 主题 ---------- */
.app-header {
  display: flex;
  align-items: flex-start;
  gap: var(--space-4);
  padding: var(--space-2) var(--space-4);
  border-block-end: 1px solid var(--color-border);
  background: var(--color-bg);
  flex: 0 0 auto;
  position: relative;
  z-index: 12;
}
.brand { display: flex; align-items: baseline; gap: var(--space-2); white-space: nowrap; }
.brand-sub { color: var(--color-text-secondary); font-size: 0.8125rem; }
.header-actions {
  flex: 0 0 auto;
  margin-inline-start: auto;
  display: flex;
  align-items: center;
  gap: var(--space-2);
}
.toolbar-toggle {
  width: 44px;
  height: 44px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--color-control-border);
  border-radius: var(--radius);
  background: var(--color-bg);
  color: var(--color-text-primary);
  cursor: pointer;
}
.toolbar-toggle svg { width: 18px; height: 18px; stroke: currentColor; stroke-width: 1.6; fill: none; transition: transform var(--motion-quick) var(--ease-standard); }
.toolbar-toggle[aria-expanded="false"] svg { transform: rotate(180deg); }
.toolbar-toggle:hover { background: var(--color-surface); border-color: var(--color-primary); }

/* 工具栏：两层语义——一级为模式分组，二级只显示当前组的工具 */
.toolbar {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 12px;                 /* 组标题与工具之间固定 12px */
  flex: 1 1 auto;
  min-width: 0;
  padding-block: var(--space-1);
  overflow: visible;
  transition: gap var(--motion-standard) var(--ease-standard), padding-block var(--motion-standard) var(--ease-standard);
}
.group-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  max-height: 64px;
  transition: max-height var(--motion-standard) var(--ease-standard), opacity var(--motion-quick) var(--ease-standard);
}

/* 一级：模式胶囊（当前组实底强调色，其余描边） */
.group-tab {
  position: relative;
  flex: 0 0 auto;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  height: 36px;
  min-height: 36px;
  padding: 0 var(--space-3);
  border: 1px solid var(--color-control-border);
  border-radius: 999px;
  background: var(--color-surface-raised);
  color: var(--color-text-primary);
  font: inherit;
  font-size: var(--text-sm);
  font-weight: 600;
  letter-spacing: normal;
  line-height: var(--lh-tight);
  cursor: pointer;
  white-space: nowrap;
  transition: background-color var(--motion-quick) var(--ease-standard),
              border-color var(--motion-quick) var(--ease-standard),
              color var(--motion-quick) var(--ease-standard);
}
.group-tab::after {
  content: "";
  position: absolute;
  inset-block: -4px;
  inset-inline: 0;
  border-radius: 999px;
}
.group-tab:hover { background: var(--color-primary-soft); border-color: var(--color-primary); }
.group-tab .group-ico { width: 1rem; height: 1rem; flex: 0 0 auto; stroke: currentColor; stroke-width: 1.4; fill: none; }
.group-tab .group-label { font-size: var(--text-sm); font-weight: 600; line-height: var(--lh-tight); letter-spacing: normal; }
.group-tab .group-caret {
  width: 12px;
  height: 12px;
  flex: 0 0 auto;
  stroke: currentColor;
  stroke-width: 1.6;
  fill: none;
  opacity: 0.55;
  transition: transform var(--motion-quick) var(--ease-standard);
}
.group-tab[aria-expanded="false"] .group-caret { transform: rotate(-90deg); }
/* 当前组：浅底 + 下划线，不再与工具 tile 争抢实底主色 */
.group-tab[aria-selected="true"] {
  background: var(--color-primary-soft);
  border-color: var(--color-primary);
  color: var(--color-text-primary);
}
.group-tab[aria-selected="true"]::before {
  content: "";
  position: absolute;
  inset-inline: 12px;
  bottom: 2px;
  height: 3px;
  border-radius: 3px;
  background: var(--color-primary);
}
.group-tab[aria-selected="true"]:hover { background: var(--color-primary-soft); }

/* 二级：当前组工具面板，固定高度避免切换时跳动 */
.tool-panels {
  display: flex;
  align-items: stretch;
  gap: 8px;
  width: 100%;
  min-width: 0;
  overflow-x: auto;
  overflow-y: visible;
  scrollbar-width: thin;
  scroll-snap-type: x proximity;
}
/* 横向溢出提示：JS 按真实几何计算两侧渐隐宽度（--fade-left/--fade-right），
   只覆盖「已经被切掉的部分」；最后一个完整标签必须在不透明区，滚到端点即无遮罩。 */
.tool-panels.scroll-right { mask-image: linear-gradient(to right, #000 calc(100% - var(--fade-right, 0px)), transparent); }
.tool-panels.scroll-left { mask-image: linear-gradient(to left, #000 calc(100% - var(--fade-left, 0px)), transparent); }
.tool-panels.scroll-left.scroll-right {
  mask-image: linear-gradient(to right, transparent, #000 var(--fade-left, 0px), #000 calc(100% - var(--fade-right, 0px)), transparent);
}
.group-tabs.scroll-right { mask-image: linear-gradient(to right, #000 calc(100% - var(--fade-right, 0px)), transparent); }
.group-tabs.scroll-left { mask-image: linear-gradient(to left, #000 calc(100% - var(--fade-left, 0px)), transparent); }
.group-tabs.scroll-left.scroll-right {
  mask-image: linear-gradient(to right, transparent, #000 var(--fade-left, 0px), #000 calc(100% - var(--fade-right, 0px)), transparent);
}
/* 滚动落点吸附到元素边界：任何静止状态标签都不许被切成半截 */
.tool-panels .tile, .tool-panels .snap-control, .tool-panels .theme-inline, .tool-panels .persistent-tools { scroll-snap-align: start; }
.group-tabs { scroll-snap-type: x proximity; }
.group-tabs .group-tab { scroll-snap-align: start; }
.tool-panel-stack {
  display: flex;
  align-items: stretch;
  gap: 8px;
  min-width: 0;
  flex: 0 0 auto;
  max-height: 64px;
  transition: max-height var(--motion-standard) var(--ease-standard), opacity var(--motion-quick) var(--ease-standard);
}
.persistent-tools {
  flex: 0 0 auto;
  display: flex;
  align-items: center;
  gap: 8px;
  padding-inline-end: 8px;
  border-inline-end: 1px solid var(--color-control-border);
}
.current-tool-label { display: none; }   /* 仅在顶栏收起且当前工具不是「选择」时显示 */
/* 折叠态当前工具：与展开态同一套 tile 字号/图标/基线，浅底描边胶囊（全局唯一实底仍是 .tool.active） */
.toolbar.is-collapsed .current-tool-label {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 4px;
  min-width: 64px;
  height: 48px;
  padding: 0 var(--space-2);
  margin-inline-start: var(--space-2);
  border: 1px solid var(--color-primary);
  border-radius: var(--radius);
  background: var(--color-primary-soft);
  color: var(--color-text-primary);
  font: inherit;
  font-size: var(--text-2xs);
  font-weight: 600;
  line-height: var(--lh-tight);
  white-space: nowrap;
  cursor: pointer;
}
.toolbar.is-collapsed .current-tool-label svg { width: 20px; height: 20px; flex: 0 0 auto; stroke: currentColor; stroke-width: 1.4; fill: none; }
.toolbar.is-collapsed .current-tool-label:hover { background: var(--color-surface); }
.tool-panel[hidden] { display: none !important; }
.tool-panel { flex: 0 0 auto; display: flex; align-items: stretch; }
.tool-panel.is-group-collapsed .tool-grid { display: none; }
.tool-grid {
  display: flex;
  align-items: stretch;
  gap: 8px;                  /* 工具间距固定 8px */
  min-height: 48px;
}
/* 顶栏收起：只留常驻选择 + 当前工具名，整行 ≤48px；展开/收起带过渡 */
.toolbar.is-collapsed { padding-block: 0; gap: 0; }
.toolbar.is-collapsed #group-tabs,
.toolbar.is-collapsed #tool-panel-stack {
  max-height: 0;
  opacity: 0;
  overflow: hidden;
  pointer-events: none;
}
.toolbar.is-collapsed #group-tabs { padding-block-end: 0; }
.toolbar.is-collapsed .tool-panels { min-height: 48px; overflow: visible; align-items: center; }
.toolbar.is-collapsed .persistent-tools { border-inline-end: 0; padding-inline-end: 0; }

/* 方形工具按钮：图标在上、文字在下，统一网格对齐 */
.tile {
  flex: 0 0 auto;
  width: 64px;
  height: 48px;
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 4px;
  padding: 0 2px;
  border: 1px solid var(--color-control-border);
  border-radius: var(--radius);
  background: var(--color-bg);
  color: var(--color-text-primary);
  font: inherit;
  font-size: var(--text-2xs);
  font-weight: 500;
  line-height: var(--lh-tight);
  white-space: nowrap;
  cursor: pointer;
  transition: background-color var(--motion-quick) var(--ease-standard),
              border-color var(--motion-quick) var(--ease-standard),
              color var(--motion-quick) var(--ease-standard);
}
.tile svg { width: 20px; height: 20px; flex: 0 0 auto; stroke: currentColor; stroke-width: 1.4; fill: none; }
.tile:hover { background: var(--color-surface); border-color: var(--color-primary); }
.tool.active {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-text);
  font-weight: 600;
}
.view-btn[aria-pressed="true"] {
  background: var(--color-primary-soft);
  border-color: var(--color-primary);
}
.tool.is-off, .view-btn.is-off { color: var(--color-text-secondary); opacity: 0.8; }

/* 吸附：总开关 + 展开 chevron，合成一个工具位 */
.snap-control {
  position: relative;
  display: inline-flex;
  align-items: stretch;
  flex: 0 0 auto;
  height: 48px;
}
.snap-toggle {
  width: 68px;
  height: 48px;
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 4px;
  padding: 0 2px;
  border: 1px solid var(--color-control-border);
  border-start-end-radius: 0;
  border-end-end-radius: 0;
  background: var(--color-bg);
  color: var(--color-text-primary);
  font: inherit;
  font-size: var(--text-2xs);
  line-height: var(--lh-tight);
  white-space: nowrap;
  cursor: pointer;
  transition: background-color var(--motion-quick) var(--ease-standard),
              border-color var(--motion-quick) var(--ease-standard);
}
.snap-toggle svg { width: 20px; height: 20px; stroke: currentColor; stroke-width: 1.4; fill: none; }
.snap-toggle[aria-pressed="true"] { background: var(--color-primary-soft); border-color: var(--color-primary); }
.snap-toggle:hover { background: var(--color-surface); border-color: var(--color-primary); }
.snap-toggle.is-off { color: var(--color-text-secondary); }
.snap-caret {
  width: 26px;
  min-width: 26px;
  height: 48px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--color-control-border);
  border-inline-start: 0;
  border-start-start-radius: 0;
  border-end-start-radius: 0;
  background: var(--color-bg);
  color: var(--color-text-secondary);
  cursor: pointer;
}
.snap-caret svg { width: 14px; height: 14px; stroke: currentColor; stroke-width: 1.6; fill: none; transition: transform var(--motion-quick) var(--ease-standard); }
.snap-caret[aria-expanded="true"] svg { transform: rotate(180deg); }
.snap-caret:hover { background: var(--color-surface); }

/* 主题：三态，作为视图组内的一个工具位 */
.theme-inline {
  flex: 0 0 auto;
  display: inline-flex;
  align-items: stretch;
  gap: 4px;
  height: 48px;
  padding: 4px;
  border: 1px solid var(--color-control-border);
  border-radius: var(--radius);
  background: var(--color-bg);
}
.theme-btn {
  width: 58px;
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 3px;
  border: 1px solid transparent;
  border-radius: 6px;
  background: transparent;
  color: var(--color-text-secondary);
  font: inherit;
  font-size: var(--text-2xs);
  line-height: var(--lh-tight);
  cursor: pointer;
}
.theme-btn svg { width: 16px; height: 16px; stroke: currentColor; stroke-width: 1.4; fill: none; }
.theme-btn:hover { background: var(--color-surface); color: var(--color-text-primary); }
.theme-btn.active { background: var(--color-primary-soft); border-color: var(--color-primary); color: var(--color-text-primary); font-weight: 600; }
.snap-menu {
  position: absolute;
  top: calc(100% + var(--space-2));
  left: 0;
  z-index: 40;
  width: 17rem;
  padding: var(--space-3);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-pop);
}
.snap-menu-title { font-size: 0.75rem; font-weight: 600; color: var(--color-text-secondary); margin-block-end: var(--space-2); }
.snap-items { display: grid; grid-template-columns: 1fr 1fr; gap: var(--space-1) var(--space-2); }
.snap-items .check { min-height: 36px; font-size: 0.8125rem; }
.snap-menu-foot { margin-block-start: var(--space-2); padding-block-start: var(--space-2); border-block-start: 1px solid var(--color-border); }
.snap-field { display: flex; align-items: center; gap: var(--space-2); font-size: 0.8125rem; color: var(--color-text-secondary); }
.snap-field input {
  width: 4.5rem;
  min-height: 36px;
  padding: 0 var(--space-2);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-bg);
  color: var(--color-text-primary);
  font: inherit;
  font-size: 0.8125rem;
}

/* ---------- 悬浮说明 ---------- */
.tool-tip {
  position: fixed;
  z-index: 60;
  max-width: 22rem;
  padding: var(--space-1) var(--space-2);
  border-radius: var(--radius-sm);
  background: var(--color-text-primary);
  color: var(--color-bg);
  font-size: 0.75rem;
  line-height: 1.45;
  box-shadow: var(--shadow-pop);
  pointer-events: none;
}

/* ---------- 布局 ---------- */
.layout {
  --eq-width: 20rem;      /* 右栏「对象与方程」宽度：分隔条拖动 / 键盘可改，默认 320px */
  --insight-h: clamp(16rem, 42vh, 26rem);
  display: grid;
  grid-template-columns: minmax(0, 1fr) var(--eq-width) calc(var(--eq-width) * 1.2);
  gap: var(--space-4);
  padding: var(--space-4);
  flex: 1 1 auto;
  min-height: 0;
  min-width: 0;
}
.layout.insight-collapsed { grid-template-columns: minmax(0, 1fr) var(--eq-width) 3rem; }

/* 分隔条：视觉 4px、指针热区 16px（触控 44px），键盘可调，焦点环可见 */
.splitter {
  position: relative;
  align-self: stretch;
  flex: 0 0 auto;
  background: transparent;
  touch-action: none;
  z-index: 8;
}
.splitter::before {
  content: "";
  position: absolute;
  border-radius: 2px;
  background: var(--color-control-border);
  transition: background-color var(--motion-quick) var(--ease-standard);
}
.splitter:hover::before,
.splitter:focus-visible::before,
.splitter.is-active::before { background: var(--color-primary); }
.splitter-v {
  position: absolute;
  inset-block: 0;
  inset-inline-end: calc(-1 * var(--space-3) - 2px);
  width: 16px;
  cursor: col-resize;
}
.splitter-v::before { inset-block: 0; inset-inline: 6px; }   /* 4px 竖线 */
.splitter-h { display: none; width: 100%; height: 12px; cursor: row-resize; }
.splitter-h::before { inset-inline: 0; inset-block: 4px; }   /* 4px 横线 */
body.is-resizing { user-select: none; -webkit-user-select: none; cursor: col-resize; }
body.is-resizing.is-resizing-h { cursor: row-resize; }

.canvas-pane {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  min-width: 0;
  min-height: 0;
}
#box {
  flex: 1 1 auto;
  width: 100%;
  height: 100%;
  min-height: 24rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--canvas-bg);
  touch-action: none;
  box-shadow: var(--shadow);
  overflow: hidden;
  /* 工具栏折叠/展开时画布尺寸平滑过渡；reduced-motion 由全局规则关闭 */
  transition: background-color var(--motion-standard) var(--ease-standard), height var(--motion-standard) var(--ease-standard);
}
#box svg { background: var(--canvas-bg); }
.hint {
  color: var(--color-text-secondary);
  font-size: 0.8125rem;
  padding-inline: var(--space-1);
  min-height: 1.5rem;
}
.snap-status {
  color: var(--color-text-secondary);
  font-size: 0.75rem;
  padding-inline: var(--space-1);
  min-height: 1.25rem;
}
.snap-status.is-off { color: var(--color-warn); }

.toast {
  position: absolute;
  left: 50%;
  right: auto;
  bottom: 3rem;
  width: max-content;
  transform: translateX(-50%) translateY(0.5rem);
  background: var(--color-text-primary);
  color: var(--color-bg);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius);
  font-size: 0.8125rem;
  max-width: min(90%, 32rem);
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--motion-quick) ease, transform var(--motion-quick) ease;
  z-index: 5;
}
.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }
/* 长按删除后的「撤销」操作条 */
.toast.has-action { pointer-events: auto; display: flex; align-items: center; gap: var(--space-2); }
.toast-action {
  appearance: none;
  border: 1px solid currentColor;
  border-radius: 6px;
  background: transparent;
  color: inherit;
  font: inherit;
  font-weight: 600;
  padding: 4px 14px;
  min-width: 44px;
  min-height: 44px;
  cursor: pointer;
}
.toast-action:hover { background: rgba(127, 127, 127, 0.18); }

/* ---------- 吸附视觉反馈 ---------- */
.snap-overlay {
  position: absolute;
  left: 0;
  top: 0;
  z-index: 6;
  width: 0;
  height: 0;
  pointer-events: none;
  transform: translate(-50%, -50%);
}
.snap-ring {
  position: absolute;
  left: -13px;
  top: -13px;
  width: 26px;
  height: 26px;
  border: 2px dashed var(--color-focus);
  border-radius: 50%;
  background: var(--color-primary-soft);
}
.snap-cross { position: absolute; background: var(--color-focus); }
.snap-cross-h { left: -18px; top: -1px; width: 36px; height: 2px; }
.snap-cross-v { left: -1px; top: -18px; width: 2px; height: 36px; }
.snap-label {
  position: absolute;
  left: 16px;
  top: -34px;
  padding: 0 var(--space-2);
  border-radius: 999px;
  background: var(--color-overlay-bg);
  border: 1px solid var(--color-border);
  color: var(--color-text-primary);
  font-size: 0.75rem;
  white-space: nowrap;
  box-shadow: var(--shadow);
}
.snap-overlay.is-tangent .snap-ring { border-style: solid; border-color: var(--color-success); }
.snap-overlay.is-tangent .snap-cross { background: var(--color-success); }
.snap-overlay.is-tangent .snap-label { border-color: var(--color-success); color: var(--color-success); font-weight: 600; }

/* ---------- 侧栏面板 ---------- */
.panel {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--space-3);
  overflow-y: auto;
  min-height: 0;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}
.panel-title { font-size: 1rem; padding-block-end: var(--space-2); border-block-end: 1px solid var(--color-border); }

/* 底部抽屉把手：桌面隐藏；≤48rem 时是抽屉收起态唯一可见的 52px 条 */
.sheet-grip { display: none; }

/* 对象列表：紧凑行、超过 8 个内部滚动，不撑高面板 */
.object-list-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--space-2);
}
.object-list-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2);
  padding: 0 4px var(--space-1);
}
.object-list-head h3 { font-size: 0.8125rem; font-weight: 600; }
.object-count {
  font-size: 0.75rem;
  color: var(--color-text-secondary);
  font-variant-numeric: tabular-nums;
}
.object-list {
  display: flex;
  flex-direction: column;
  gap: 2px;
  max-height: 254px;          /* 8 行 × 30px + 间隙 */
  overflow-y: auto;
  overscroll-behavior: contain;
}
.object-list .empty { margin: 0; padding: 4px; font-size: 0.8125rem; }
.object-row {
  display: flex;
  align-items: center;
  gap: 8px;
  width: 100%;
  height: 30px;
  min-height: 30px;
  padding: 0 8px;
  border: 1px solid transparent;
  border-radius: 6px;
  background: transparent;
  color: var(--color-text-primary);
  font: inherit;
  font-size: 0.8125rem;
  text-align: start;
  cursor: pointer;
}
.object-row:hover { background: var(--color-surface); }
.object-row.is-selected { background: var(--color-primary-soft); border-color: var(--color-primary); }
.obj-type {
  flex: 0 0 auto;
  width: 20px;
  height: 20px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 4px;
  background: var(--color-surface);
  color: var(--color-text-secondary);
  font-size: 0.6875rem;
  font-weight: 600;
  line-height: 1;
}
.object-row.is-selected .obj-type { background: var(--color-bg); color: var(--color-text-primary); }
.obj-name { flex: 1 1 auto; min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; font-weight: 500; }
.obj-state { flex: 0 0 auto; font-size: 0.6875rem; color: var(--color-text-secondary); }
/* 触控设备把行高提升到 44px 以满足最小热区；精细指针保留 30px 紧凑密度 */
@media (pointer: coarse) {
  .object-row { height: 44px; min-height: 44px; }
  .object-list { max-height: 358px; }
  /* 分隔条触控热区 44px（视觉线仍为 4px） */
  .splitter-v { width: 44px; inset-inline-end: -38px; }
  .splitter-v::before { inset-inline: 22px; }
  .splitter-h { height: 44px; }
  .splitter-h::before { inset-block: 20px; }
}

.panel-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--space-3);
}
.panel-card h3 { margin-block-end: var(--space-2); }

/* 行内容放不下时换行，而不是把按钮文字挤出卡片 */
.row { display: flex; flex-wrap: wrap; align-items: center; gap: var(--space-2); margin-block-end: var(--space-2); }
.row.wrap { flex-wrap: wrap; }
.row:last-child { margin-block-end: 0; }
.field-label { color: var(--color-text-secondary); font-size: var(--text-sm); line-height: var(--lh-tight); white-space: nowrap; }
input[type="text"], input[type="number"] {
  min-height: 44px;
  padding: 0 var(--space-2);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  font: inherit;
  font-size: var(--text-md);
  line-height: var(--lh-tight);
  color: var(--color-text-primary);
  background: var(--color-bg);
  min-width: 0;
  flex: 1;
}
input[type="text"].short { max-width: 5.5rem; flex: 0 0 auto; }
.input-error, .error-text { color: var(--color-error); font-size: 0.8125rem; }

.math-field {
  flex: 1;
  min-width: 0;
  height: 44px;
  min-height: 44px;
  padding: 0 var(--space-2);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-bg);
  /* 与普通输入框同一字号/行高，避免同一张卡片里公式比文字大一号 */
  font-size: var(--text-md);
  line-height: var(--lh-tight);
  /* 虚拟键盘按键最小 44px 热区 */
  --keycap-height: 44px;
}
math-field::part(menu-toggle) { display: none; }

.btn {
  min-height: 44px;
  min-width: 44px;
  padding: 0 var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-bg);
  color: var(--color-text-primary);
  font: inherit;
  font-size: var(--text-sm);
  line-height: var(--lh-tight);
  cursor: pointer;
  white-space: nowrap;
  transition: background-color var(--motion-quick) ease, border-color var(--motion-quick) ease;
}
.btn:hover { background: var(--color-surface); }
.btn.danger { color: var(--color-error); border-color: var(--color-error); }
.btn.danger:hover { background: var(--color-error-soft); }

.symbols { display: flex; flex-wrap: wrap; gap: var(--space-1); margin-block-end: var(--space-2); }
.symbols button {
  min-width: 44px;
  min-height: 44px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-bg);
  color: var(--color-text-primary);
  font-size: 1rem;
  font-family: var(--font-sans);
  cursor: pointer;
}
.symbols button:hover { background: var(--color-surface); }

.check { display: flex; align-items: center; gap: var(--space-2); font-size: 0.875rem; min-height: 44px; color: var(--color-text-primary); }
.count { color: var(--color-text-secondary); font-weight: 400; font-size: 0.8125rem; }
.tiny { color: var(--color-text-secondary); font-size: 0.75rem; margin-block-start: var(--space-1); }
.empty { color: var(--color-text-secondary); font-size: 0.8125rem; }

.results { display: flex; flex-direction: column; gap: var(--space-2); }
.result-item {
  border-inline-start: 3px solid var(--color-primary);
  padding-inline-start: var(--space-2);
  font-size: 0.875rem;
}
.result-item strong { font-variant-numeric: tabular-nums; font-family: var(--font-mono); }
.result-label { color: var(--color-text-secondary); font-size: 0.75rem; display: block; }

.constraint-list { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: var(--space-1); }
.constraint-item {
  display: flex;
  align-items: flex-start;
  gap: var(--space-2);
  padding: var(--space-1) var(--space-2);
  border: 1px solid var(--color-border);
  border-inline-start: 3px solid var(--color-success);
  border-radius: var(--radius);
  background: var(--color-bg);
  font-size: 0.8125rem;
}
.constraint-item .constraint-text { flex: 1; min-width: 0; overflow-wrap: anywhere; }
.constraint-item .constraint-err { display: block; color: var(--color-text-secondary); font-size: 0.75rem; font-variant-numeric: tabular-nums; }
.constraint-item button {
  min-height: 44px;
  min-width: 44px;
  border: 1px solid var(--color-border);
  border-radius: 0.25rem;
  background: var(--color-bg);
  color: var(--color-error);
  font-size: 0.75rem;
  cursor: pointer;
}
.constraint-item button:hover { background: var(--color-error-soft); }

.equation-list { display: flex; flex-direction: column; gap: var(--space-2); }
.equation-item { border: 1px solid var(--color-border); border-radius: var(--radius); padding: var(--space-2); background: var(--color-bg); }
.equation-head { display: flex; align-items: center; gap: var(--space-2); margin-block-end: var(--space-1); }
.equation-name { font-weight: 600; font-size: 0.8125rem; }
.eq-line {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 0.8125rem;
  overflow-wrap: anywhere;
  color: var(--color-text-primary);
  padding-block: var(--space-1);
}
.copy-btn {
  margin-inline-start: auto;
  min-height: 44px;
  padding-inline: var(--space-2);
  border: 1px solid var(--color-border);
  background: var(--color-bg);
  border-radius: 0.25rem;
  color: var(--color-text-primary);
  font-size: 0.75rem;
  cursor: pointer;
}

/* ---------- 一键结论面板 ---------- */
.insight-head { display: flex; align-items: center; justify-content: space-between; gap: var(--space-2); flex-wrap: wrap; }
.insight-head .panel-title { border-block-end: 0; padding-block-end: 0; }
.insight-head-actions { display: flex; align-items: center; gap: var(--space-2); }
.segmented { display: flex; border: 1px solid var(--color-border); border-radius: var(--radius); overflow: hidden; }
.seg {
  min-height: 36px;
  padding: 0 var(--space-2);
  border: 0;
  background: var(--color-bg);
  color: var(--color-text-secondary);
  font: inherit;
  font-size: 0.8125rem;
  cursor: pointer;
}
.seg.active { background: var(--color-primary-soft); color: var(--color-text-primary); border: 1px solid var(--color-primary); font-weight: 600; margin: -1px; }
.icon-btn {
  height: 36px;
  min-height: 36px;
  padding: 0 var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: 999px;
  background: var(--color-surface-raised);
  color: var(--color-text-secondary);
  font: inherit;
  font-size: 0.8125rem;
  cursor: pointer;
}
.icon-btn:hover { background: var(--color-primary-soft); color: var(--color-text-primary); border-color: var(--color-primary); }

.insight-body { display: flex; flex: 1 1 auto; flex-direction: column; gap: var(--space-3); overflow-y: auto; -webkit-overflow-scrolling: touch; min-height: 0; padding-block-start: var(--space-2); overscroll-behavior: contain; }
.insight-identity {
  background: var(--color-surface-raised);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-3);
}
.identity-main { display: flex; align-items: center; gap: var(--space-2); flex-wrap: wrap; }
.identity-main h3 { font-size: var(--text-md); font-weight: 700; line-height: var(--lh-tight); }
.type-badge {
  display: inline-block;
  padding: 0.125rem var(--space-2);
  border-radius: 999px;
  border: 1px solid var(--color-primary);
  color: var(--color-primary);
  background: var(--color-primary-soft);
  font-size: 0.75rem;
  font-weight: 600;
  white-space: nowrap;
}
.identity-state { margin-inline-start: auto; font-size: 0.75rem; color: var(--color-text-secondary); }
.identity-meta { margin-block-start: var(--space-1); font-size: 0.8125rem; color: var(--color-text-secondary); font-variant-numeric: tabular-nums; }
.identity-guide { margin-block-start: var(--space-2); font-size: 0.8125rem; color: var(--color-text-primary); }

.eq-details {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-surface-raised);
  overflow: hidden;
}
.eq-details > summary {
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2);
  min-height: 44px;
  padding: var(--space-2) var(--space-3);
  cursor: pointer;
}
.eq-details > summary::-webkit-details-marker { display: none; }
.eq-sum-label { flex: 0 0 auto; font-size: 0.75rem; font-weight: 600; color: var(--color-text-secondary); }
.eq-sum-value { font-family: var(--font-mono); font-variant-numeric: tabular-nums; font-size: 0.8125rem; text-align: end; overflow-wrap: anywhere; }
.eq-expand { padding: 0 var(--space-3) var(--space-2); border-block-start: 1px solid var(--color-border); }
.eq-expand .eq-line { padding-block: var(--space-1); }
.warn-text { margin-block-start: var(--space-1); color: var(--color-warn); font-size: 0.75rem; }

.insight-related { display: flex; flex-direction: column; gap: var(--space-2); }
.section-head { display: flex; align-items: baseline; justify-content: space-between; gap: var(--space-2); font-size: 0.8125rem; font-weight: 600; }
.insight-all { border-block-start: 1px solid var(--color-border); padding-block-start: var(--space-2); }
.insight-all > summary {
  list-style: none;
  display: flex;
  align-items: center;
  min-height: 44px;
  padding: 0 var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-surface-raised);
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
}
.insight-all > summary::-webkit-details-marker { display: none; }
.insight-all > summary:hover { border-color: var(--color-primary); }
.insight-all .cards { margin-block-start: var(--space-2); }
.link-btn {
  align-self: flex-start;
  min-height: 44px;
  padding: var(--space-2) 0;
  border: 0;
  background: none;
  color: var(--color-primary);
  font: inherit;
  font-size: 0.8125rem;
  text-decoration: underline;
  cursor: pointer;
}

.cards { display: flex; flex-direction: column; gap: var(--space-3); }
.card {
  background: var(--color-surface-raised);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-4);
  box-shadow: var(--card-shadow);
}
.card.card-warn { border-color: var(--color-warn); background: var(--color-warn-bg); }
.card-head { display: flex; align-items: flex-start; justify-content: space-between; gap: var(--space-2); margin-block-end: var(--space-2); }
.card-title { display: flex; align-items: center; gap: var(--space-2); flex-wrap: wrap; min-width: 0; }
.card-title h3 { font-size: 0.8125rem; font-weight: 600; }
/* 徽标改为纯文字，不再用底色块抢占视觉层级 */
.badge {
  display: inline;
  padding: 0;
  border: 0;
  border-radius: 0;
  background: none;
  color: var(--color-text-secondary);
  font-size: 0.75rem;
  font-weight: 600;
  white-space: nowrap;
}
.card-warn .badge { background: none; color: var(--color-warn); }
.card-more {
  flex: 0 0 auto;
  width: 36px;
  height: 36px;
  min-width: 36px;
  border: 1px solid var(--color-border);
  border-radius: 999px;
  background: var(--color-bg);
  color: var(--color-text-secondary);
  font: inherit;
  font-size: 1rem;
  line-height: 1;
  cursor: pointer;
}
.card-more:hover { background: var(--color-primary-soft); color: var(--color-text-primary); border-color: var(--color-primary); }
.conclusion { margin-block-end: var(--space-2); font-size: 1rem; line-height: 1.5; }

/* 二级：关键数值一行紧凑、等宽数字、右对齐 */
.card-metrics { display: flex; flex-direction: column; gap: 2px; padding-block: var(--space-2); border-block: 1px solid var(--color-border); }
.kv-row { display: flex; align-items: baseline; justify-content: space-between; gap: var(--space-3); font-size: 0.8125rem; }
.kv-label { flex: 0 1 auto; color: var(--color-text-secondary); text-align: start; }
.kv-value { margin-inline-start: auto; font-family: var(--font-mono); font-variant-numeric: tabular-nums; text-align: end; overflow-wrap: anywhere; }

/* 三级：推导 / 系数明细默认收起 */
.card-details { margin-block-start: var(--space-2); }
.card-details > summary {
  list-style: none;
  display: inline-flex;
  align-items: center;
  gap: 4px;
  min-height: 36px;
  padding: 0 var(--space-2);
  border: 1px solid var(--color-border);
  border-radius: 999px;
  background: var(--color-bg);
  color: var(--color-text-secondary);
  font-size: 0.75rem;
  cursor: pointer;
}
.card-details > summary::-webkit-details-marker { display: none; }
.card-details > summary::before { content: "＋"; }
.card-details[open] > summary::before { content: "－"; }
.card-details > summary:hover { color: var(--color-text-primary); border-color: var(--color-primary); }
.details-body { margin-block-start: var(--space-2); padding-block-start: var(--space-1); border-block-start: 1px solid var(--color-border); }
.sub-title { font-size: 0.8125rem; font-weight: 600; color: var(--color-text-secondary); margin-block: var(--space-2) var(--space-1); }
.card .eq-line { background: var(--color-surface); border-radius: 0.25rem; padding: var(--space-1) var(--space-2); margin-block: var(--space-1); }
.card.is-linked { border-color: var(--color-primary); box-shadow: 0 0 0 2px var(--color-primary-soft); }

/* 卡片菜单 */
.card-menu {
  position: fixed;
  z-index: 70;
  min-width: 15rem;
  padding: var(--space-1);
  display: flex;
  flex-direction: column;
  gap: 2px;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-pop);
}
.card-menu [role="menuitem"] {
  display: block;
  width: 100%;
  min-height: 40px;
  padding: 6px var(--space-3);
  border: 0;
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--color-text-primary);
  font: inherit;
  font-size: 0.875rem;
  text-align: start;
  cursor: pointer;
}
.card-menu [role="menuitem"]:hover, .card-menu [role="menuitem"]:focus-visible { background: var(--color-primary-soft); }
.card-menu [role="menuitem"].danger { color: var(--color-error); }
.card-menu [role="menuitem"]:disabled { opacity: 0.45; cursor: not-allowed; }

/* 右栏整体折叠 */
.panel-insight { overflow: hidden; }
.panel-insight.is-collapsed { padding: 0; gap: 0; align-items: center; justify-content: center; }
.panel-insight.is-collapsed .insight-head,
.panel-insight.is-collapsed .insight-body { display: none; }
.insight-reopen {
  writing-mode: vertical-rl;
  text-orientation: upright;
  min-height: 100%;
  padding: var(--space-3) 0;
  border: 0;
  background: transparent;
  color: var(--color-text-secondary);
  font: inherit;
  font-size: 0.875rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  cursor: pointer;
}
.insight-reopen:hover { background: var(--color-primary-soft); color: var(--color-text-primary); }

.meter { margin-block-start: var(--space-2); }
.meter-track { display: block; position: relative; height: 0.5rem; background: var(--color-surface); border: 1px solid var(--color-border); border-radius: 999px; }
.meter-dot { position: absolute; top: -0.25rem; width: 0.125rem; height: 1rem; background: var(--color-text-primary); }
.meter-scale { display: flex; justify-content: space-between; font-size: 0.6875rem; color: var(--color-text-secondary); font-variant-numeric: tabular-nums; }

.rangebar { position: relative; height: 0.75rem; background: var(--color-surface); border: 1px solid var(--color-border); border-radius: 999px; margin-block-start: var(--space-2); }
.range-ok { position: absolute; top: 0; bottom: 0; background: var(--color-success-soft); border-inline: 1px solid var(--color-success); }
.range-marker { position: absolute; top: -0.25rem; width: 0.125rem; height: 1.25rem; background: var(--color-text-primary); }

.card.is-linked { border-color: var(--color-primary); box-shadow: 0 0 0 2px var(--color-primary-soft); }

:focus-visible {
  outline: 3px solid var(--color-focus);
  outline-offset: 2px;
}
#box:focus-visible { outline-offset: -3px; }

.kv-value, .eq-line, .result-item strong, .meter-scale { font-variant-numeric: tabular-nums; }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

@media (prefers-contrast: more) {
  :root {
    --color-text-secondary: #000000;
    --color-border: rgba(60, 60, 67, 0.6);
    --color-control-border: #000000;
    --color-secondary-background: #ffffff;
  }
  :root[data-theme="dark"] {
    --color-text-secondary: #ffffff;
    --color-border: rgba(255, 255, 255, 0.6);
    --color-control-border: #ffffff;
    --color-secondary-background: #000000;
  }
  :root[data-theme="dark"] .card,
  :root[data-theme="dark"] .panel-card { border-width: 2px; }
}

@media (max-width: 72rem) {
  /* 两栏：画布在左；右栏内部纵向堆叠「对象与方程 / 分隔条 / 一键结论」 */
  .layout {
    grid-template-columns: minmax(0, 1fr) var(--eq-width);
    grid-template-rows: minmax(0, 1fr) 12px auto;
    min-height: 0;
  }
  .canvas-pane { grid-column: 1; grid-row: 1 / span 3; min-height: 0; }
  /* 画布可收缩：不再用 60vh 撑破父容器，避免覆盖右栏 */
  #box { min-height: 0; }
  #panel-equations, .panel-equations { grid-column: 2; grid-row: 1; }
  .splitter-h { display: block; grid-column: 2; grid-row: 2; }
  #panel-insight, .panel-insight { grid-column: 2; grid-row: 3; height: var(--insight-h); max-height: none; min-height: 0; }
  .layout.insight-collapsed { grid-template-columns: minmax(0, 1fr) var(--eq-width); }
  .layout.insight-collapsed .panel-insight.is-collapsed { grid-column: 2; height: 3rem; max-height: 3rem; min-height: 3rem; flex-direction: row; }
}

@media (max-width: 48rem), (max-height: 30rem) {
  .app-header { flex-wrap: wrap; align-items: flex-start; gap: var(--space-2); padding-block-end: var(--space-2); }
  .brand { flex: 1 1 auto; order: 1; }
  .header-actions { order: 2; }
  /* 工具区回到顶栏第二行；收起时只有一条 48px 行 */
  .toolbar { order: 3; flex: 1 1 100%; width: 100%; align-items: stretch; gap: 8px; min-width: 0; overflow: visible; }
  /* 分组行：四个标签收缩成一行铺满，永不横向滚动，保证「基本/构造/测量/视图」都完整显示 */
  .group-tabs { flex-wrap: nowrap; overflow-x: visible; padding-block-end: 2px; flex: 1 1 auto; min-width: 0; gap: 4px; }
  .group-tabs .group-tab { flex: 1 1 0; min-width: 0; padding-inline: 6px; gap: 4px; justify-content: center; }
  .group-tabs .group-caret { display: none; }
  .group-tabs .group-label { flex: 0 1 auto; min-width: 0; overflow: hidden; text-overflow: ellipsis; }
  /* 工具行：可横滑 + 强制吸附到整块 tile，静止时不会停在半个标签上；边缘渐隐由 JS 控制 */
  .tool-panels { overflow-x: auto; scroll-snap-type: x mandatory; overscroll-behavior-x: contain; -webkit-overflow-scrolling: touch; }
  .tool-panels .tile, .tool-panels .snap-control, .tool-panels .theme-inline, .tool-panels .persistent-tools { scroll-snap-stop: always; }
  /* 紧凑视口统一用页头循环按钮；「视图」组里的三态按钮不占位 */
  .theme-inline { display: none; }
  .theme-cycle { display: inline-flex !important; }
  /* 结论说明区（相关结论 / 点卡片可选中对象）在内容滚动时固定在内容区顶部 */
  #insight-related .section-head {
    position: sticky;
    top: 0;
    z-index: 1;
    background: var(--color-bg);
    padding-block: 2px;
  }
  .snap-menu { top: auto; bottom: calc(100% + var(--space-2)); box-shadow: var(--shadow-pop); }

  .layout {
    grid-template-columns: minmax(0, 1fr);
    grid-template-rows: minmax(0, 1fr);
    padding: var(--space-2);
    padding-block-end: calc(3.5rem + env(safe-area-inset-bottom));
    gap: var(--space-2);
  }
  .canvas-pane { grid-column: 1; grid-row: 1; min-height: 0; overflow: visible; }
  #box { min-height: 45vh; }
  .splitter-v, .splitter-h { display: none; }
  #panel-equations, #panel-insight { grid-column: auto; grid-row: auto; }

  /* 两个右栏面板改为底部抽屉：收起只露 52px 把手，展开最高 60vh */
  .panel {
    position: fixed;
    bottom: 0;
    width: 50%;
    height: min(60vh, calc(100dvh - 12rem));
    max-height: none;
    padding: 0 12px calc(12px + env(safe-area-inset-bottom));
    border-radius: var(--radius-md) var(--radius-md) 0 0;
    border-color: var(--color-control-border);
    background: var(--color-bg);
    box-shadow: var(--shadow-pop);
    transform: translateY(calc(100% - 52px));
    transition: transform var(--motion-standard) var(--ease-standard), width var(--motion-quick) var(--ease-standard);
    overscroll-behavior: contain;
    z-index: 28;
  }
  #panel-equations { left: 0; height: min(60vh, calc(100dvh - 12rem)); }
  #panel-insight { left: 50%; height: min(60vh, calc(100dvh - 12rem)); min-height: 0; }
  #panel-insight.is-collapsed { height: min(60vh, calc(100dvh - 12rem)); max-height: none; min-height: 0; flex-direction: column; align-items: stretch; justify-content: flex-start; }
  /* 展开必须全宽：用 inset-inline 覆盖 left/right，逻辑方向同时适配 LTR/RTL */
  #panel-equations.sheet-open, #panel-insight.sheet-open, .panel.sheet-open {
    inset-inline: 0;
    width: 100%;
    max-width: 100vw;
    transform: translateY(0);
    z-index: 30;
  }

  .sheet-grip {
    display: block;
    position: sticky;
    top: 0;
    z-index: 2;
    margin-inline: -12px;
    background: var(--color-bg);
  }
  .sheet-toggle {
    position: relative;
    width: 100%;
    height: 52px;
    padding: 10px 14px 0;
    display: flex;
    align-items: center;
    gap: 8px;
    border: 0;
    border-radius: var(--radius-md) var(--radius-md) 0 0;
    background: transparent;
    color: var(--color-text-primary);
    font: inherit;
    text-align: start;
    cursor: pointer;
    touch-action: none;
  }
  .sheet-toggle:hover { background: var(--color-surface); }
  .sheet-bar {
    position: absolute;
    top: 6px;
    left: 50%;
    transform: translateX(-50%);
    width: 36px;
    height: 4px;
    border-radius: 2px;
    background: var(--color-control-border);
  }
  .sheet-title { font-size: 0.9375rem; font-weight: 600; }
  .sheet-chevron {
    width: 16px;
    height: 16px;
    margin-inline-start: auto;
    stroke: currentColor;
    stroke-width: 1.6;
    fill: none;
    transition: transform var(--motion-quick) var(--ease-standard);
  }
  .sheet-toggle[aria-expanded="true"] .sheet-chevron { transform: rotate(180deg); }
  .panel-insight #btn-insight-collapse { display: none; }
  .panel-insight.is-collapsed .insight-reopen { display: none; }

  /* 抽屉内已有标题，隐藏面板自带的重复标题 */
  #eq-heading, #insight-heading { display: none; }
  /* 抽屉顶部不许留空白：头部只留模式切换，内容与把手之间收紧 */
  .insight-head { justify-content: flex-end; padding-block: 0; }
  .panel { gap: var(--space-2); }
  .insight-body { padding-block-start: 0; gap: var(--space-2); }
  /* 滚到最底时放掉吸顶说明区：否则最后一张相关结论的 24px 公式行会停在内容区
     顶部被吸顶头盖住（实测重叠 23.5px、elementFromPoint 命中 HEAD）。到底时隐藏
     26.5px 高的说明区，最大 scrollTop 随之减小，末卡公式行完整落到吸顶区下方；
     上滚离开底部即恢复吸顶。 */
  #insight-body.at-end #insight-related .section-head { display: none; }

  /* 触屏热区统一 ≥44px */
  .group-tab { height: 44px; min-height: 44px; }
  .snap-caret { width: 44px; min-width: 44px; }
  .theme-inline { padding: 0; }
  .theme-btn { min-height: 48px; }
  .seg { min-height: 44px; }
  .icon-btn { height: 44px; min-height: 44px; }
  .card-more { width: 44px; height: 44px; min-width: 44px; }
  .object-row { height: 44px; min-height: 44px; }
  .object-list { max-height: 358px; }
  .card-details > summary, .eq-details > summary, .insight-all > summary { min-height: 44px; display: flex; align-items: center; }

  .toast { bottom: calc(3.5rem + 0.5rem); }
  .tool-tip { display: none; }
}

/* 横屏（高度 ≤30rem）：顶栏压缩成一行；抽屉加高但不得盖住顶栏；主题三态收成单个循环按钮 */
@media (max-height: 30rem) {
  .app-header { flex-wrap: nowrap; align-items: center; }
  .brand { order: 1; flex: 0 1 auto; }
  .toolbar { order: 2; flex: 1 1 auto; width: auto; margin-inline: var(--space-2); }
  .header-actions { order: 3; }
  /* 抽屉展开高度：100dvh 减去展开态顶栏(≈8.5rem) 的预留，保证抽屉顶不压顶栏 */
  #panel-equations, #panel-insight, #panel-insight.is-collapsed {
    height: min(65vh, calc(100dvh - 8.5rem));
  }
  /* 提示行必须停在抽屉把手上方：画布列改成可收缩的纵向 flex，
     去掉 45vh 最小高度，让 #box 让位给 snap-status + hint */
  .canvas-pane { display: flex; flex-direction: column; min-height: 0; }
  #box { flex: 1 1 auto; min-height: 0; }
  #snap-status, #hint { flex: 0 0 auto; }
  /* 对象抽屉：压缩把手/卡片内边距，44px 行高下首屏至少 4 行 */
  #panel-equations { padding-block-end: 4px; }
  .sheet-toggle { height: 44px; padding: 4px 14px 0; }
  .object-list-card { padding: 4px; }
  .object-list-head { padding: 0 4px 0; }
  .object-list { gap: 0; max-height: none; }
  .object-row { height: 44px; min-height: 44px; }
}

/* 竖屏：品牌与「主题循环 + 折叠」必须同一行，避免主题按钮单独撑出一整行 */
@media (max-width: 48rem) {
  .brand { flex: 1 1 0; min-width: 0; overflow: hidden; }
  .brand-sub { display: none; }
  /* 纵向内边距 8px→6px：页头收起 117 / 展开 179，回到第七轮水平 */
  .app-header { padding-block: 6px; }
}

/* MathLive 默认 10 列：390 宽下键宽 37、中心距 39。
   隐藏分组分隔条并两端对齐后，9 键行铺满 390，实测相邻键中心距 44.1px；
   键宽仍 37px 属明确降级（见 README「已知限制」）。
   MathLive 用 adoptedStyleSheets 注入 `.MLK__rows > .MLK__row { justify-content:center }`，
   与 `.ML__keyboard .MLK__row` 同权重且后置，不用 !important 会被覆盖（实测仍 center、pitch 39）。 */
@media (max-width: 48rem) {
  .ML__keyboard .MLK__row { justify-content: space-between !important; margin-inline: -1px; width: calc(100% + 2px); }
  .ML__keyboard .MLK__row > .separator { display: none !important; }
}