:root {
  --bg: #f6f8fb;
  --card: #ffffff;
  --border: #e6e9ef;
  --text: #1f2937;
  --muted: #6b7280;
  --accent: #2563eb;
  --accent-soft: #eff4ff;
  --ok: #16a34a;
  --ok-soft: #f0fdf4;
  --bad: #dc2626;
  --bad-soft: #fef2f2;
  --shadow: 0 1px 3px rgba(16,24,40,.06), 0 8px 24px rgba(16,24,40,.05);

  /* 各单位颜色：从小到大，正好一道彩虹 */
  --u-mm: #f97316;   /* 橙 */
  --u-cm: #f59e0b;   /* 琥珀 */
  --u-dm: #10b981;   /* 绿 */
  --u-m:  #3b82f6;   /* 蓝 */
  --u-km: #8b5cf6;   /* 紫 */
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  -webkit-text-size-adjust: 100%;
}

.topbar {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 16px 24px;
  background: var(--card);
  border-bottom: 1px solid var(--border);
}
.topbar h1 { font-size: 18px; margin: 0; font-weight: 600; }
.back { color: var(--muted); text-decoration: none; font-size: 14px; white-space: nowrap; }
.back:hover { color: var(--accent); }

.wrap {
  max-width: 1080px;
  margin: 0 auto;
  padding: 28px 24px 72px;
  display: flex;
  flex-direction: column;
  gap: 22px;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 22px 24px 24px;
  box-shadow: var(--shadow);
}
.card > h2 { margin: 0 0 14px; font-size: 17px; }
.card > h2:not(:first-child) { margin-top: 4px; }
.hint { color: var(--muted); font-size: 12.5px; margin: 0 0 16px; }

/* 按钮 */
.btn {
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--text);
  padding: 8px 14px;
  border-radius: 9px;
  font-size: 14px;
  font-family: inherit;
  cursor: pointer;
  transition: background .15s, border-color .15s, transform .05s;
}
.btn:active { transform: translateY(1px); }
.btn:disabled { opacity: .45; cursor: not-allowed; }
.btn-primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn-primary:hover { background: #1d4ed8; border-color: #1d4ed8; }

/* ① 单位家族 */
.family { display: flex; flex-direction: column; gap: 10px; }
.fam-item {
  border: 1px solid var(--border);
  border-radius: 14px;
  overflow: hidden;
  background: #fff;
  transition: border-color .2s, box-shadow .2s;
}
.fam-item.open { border-color: var(--uc); box-shadow: 0 6px 18px rgba(16,24,40,.07); }
.fam-head {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 12px 16px;
  cursor: pointer;
  user-select: none;
}
.fam-emoji {
  width: 46px; height: 46px; flex: 0 0 46px;
  border-radius: 12px;
  display: flex; align-items: center; justify-content: center;
  font-size: 26px;
  background: color-mix(in srgb, var(--uc) 14%, #fff);
}
.fam-name { font-size: 17px; font-weight: 700; color: var(--uc); }
.fam-sym { font-size: 13px; color: var(--muted); margin-left: 4px; font-weight: 500; }
.fam-tag { margin-left: auto; font-size: 13px; color: var(--muted); display: flex; align-items: center; gap: 6px; }
.fam-caret { transition: transform .25s ease; font-size: 12px; }
.fam-item.open .fam-caret { transform: rotate(90deg); }

.fam-body {
  display: grid;
  grid-template-rows: 0fr;
  transition: grid-template-rows .3s ease;
}
.fam-item.open .fam-body { grid-template-rows: 1fr; }
.fam-body-inner { overflow: hidden; }
.fam-detail {
  padding: 4px 16px 18px 76px;
  font-size: 14.5px;
  line-height: 1.85;
  color: var(--text);
}
.fam-detail .rel { color: var(--uc); font-weight: 700; }
.fam-detail .ex {
  display: inline-flex; align-items: center; gap: 6px;
  margin-top: 6px;
  padding: 4px 10px;
  border-radius: 999px;
  background: color-mix(in srgb, var(--uc) 10%, #fff);
  color: var(--uc);
  font-size: 13.5px;
  font-weight: 600;
}
@media (max-width: 560px) { .fam-detail { padding-left: 16px; } }

/* ② 长度阶梯对比图（对数条） */
.ladder { display: flex; flex-direction: column; gap: 12px; }
.lad-row {
  display: grid;
  grid-template-columns: 92px 1fr;
  gap: 12px;
  align-items: center;
  cursor: pointer;
  padding: 4px;
  border-radius: 10px;
  transition: background .15s;
}
.lad-row:hover { background: #f7f9ff; }
.lad-label { display: flex; align-items: center; gap: 7px; font-size: 14px; font-weight: 600; }
.lad-emoji { font-size: 20px; }
.lad-track {
  position: relative;
  height: 30px;
  background: #f3f5f9;
  border-radius: 8px;
  overflow: hidden;
}
.lad-fill {
  position: absolute; left: 0; top: 0; bottom: 0;
  border-radius: 8px 0 0 8px;
  background: linear-gradient(90deg, color-mix(in srgb, var(--uc) 55%, #fff), var(--uc));
  width: 0;
  transition: width .8s cubic-bezier(.22,.61,.36,1);
}
.lad-fill .lad-cap {
  position: absolute; right: 8px; top: 50%; transform: translateY(-50%);
  font-size: 12px; color: #fff; font-weight: 600; white-space: nowrap;
  text-shadow: 0 1px 2px rgba(0,0,0,.18);
}
.lad-note { grid-column: 2; font-size: 12px; color: var(--muted); margin-top: -4px; }

/* ③ 三维缩放剧场 */
.theater .stage3d {
  position: relative;
  height: 380px;
  border-radius: 16px;
  background:
    radial-gradient(120% 120% at 50% 8%, #eaf0ff 0%, #f4f7ff 45%, #fbfcff 100%);
  border: 1px solid var(--border);
  overflow: hidden;
  perspective: 1100px;
  perspective-origin: 50% 42%;
}
.ground-shadow {
  position: absolute; left: 50%; top: 60%;
  width: 62%; height: 80px;
  transform: translate(-50%, -50%);
  background: radial-gradient(ellipse at center, rgba(16,24,40,.20), rgba(16,24,40,0) 70%);
  filter: blur(2px);
}
.world-cam {
  position: absolute; left: 50%; top: 46%;
  transform: translate(-50%, -50%) scale(var(--cam, 1));
  transition: transform .65s cubic-bezier(.34,1.25,.5,1);
  transform-style: preserve-3d;
}
.world {
  transform-style: preserve-3d;
  animation: spin 22s linear infinite;
}
@keyframes spin {
  from { transform: rotateX(-14deg) rotateY(0deg); }
  to   { transform: rotateX(-14deg) rotateY(360deg); }
}
.bar3d {
  --bd: 48px;   /* 进深 */
  --bh: 48px;   /* 厚度/高度 */
  position: relative;
  width: var(--len, 120px);
  height: var(--bh);
  transform-style: preserve-3d;
  transition: width .65s cubic-bezier(.34,1.25,.5,1);
}
.face { position: absolute; transition: left .65s cubic-bezier(.34,1.25,.5,1), top .65s cubic-bezier(.34,1.25,.5,1); }
.f-front, .f-back  { width: var(--len); height: var(--bh); }
.f-left,  .f-right { width: var(--bd);  height: var(--bh); }
.f-top,   .f-bottom{ width: var(--len); height: var(--bd); }
.f-front  { background: var(--bar); transform: translateZ(calc(var(--bd) / 2)); }
.f-back   { background: color-mix(in srgb, var(--bar) 78%, #000); transform: rotateY(180deg) translateZ(calc(var(--bd) / 2)); }
.f-right  { background: color-mix(in srgb, var(--bar) 60%, #000); transform: rotateY(90deg)  translateZ(calc(var(--len) / 2)); left: calc((var(--len) - var(--bd)) / 2); }
.f-left   { background: color-mix(in srgb, var(--bar) 70%, #000); transform: rotateY(-90deg) translateZ(calc(var(--len) / 2)); left: calc((var(--len) - var(--bd)) / 2); }
.f-top    { background: color-mix(in srgb, var(--bar) 88%, #fff); transform: rotateX(90deg)  translateZ(calc(var(--bh) / 2)); top: calc((var(--bh) - var(--bd)) / 2); }
.f-bottom { background: color-mix(in srgb, var(--bar) 62%, #000); transform: rotateX(-90deg) translateZ(calc(var(--bh) / 2)); top: calc((var(--bh) - var(--bd)) / 2); }

/* 比例尺：固定的「你」做参照 */
.human {
  position: absolute; right: 7%; bottom: 11%;
  font-size: 56px; line-height: 1; text-align: center;
  filter: drop-shadow(0 6px 8px rgba(16,24,40,.18));
  z-index: 3;
}
.human-cap { display: block; font-size: 11px; color: var(--muted); margin-top: 2px; white-space: nowrap; }
.bar-cap {
  position: absolute; left: 50%; top: 12px; transform: translateX(-50%);
  background: rgba(255,255,255,.82);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 3px 13px;
  font-size: 13px; font-weight: 600; color: var(--text);
  z-index: 3; white-space: nowrap;
}
.rels { font-size: 12.5px; color: var(--accent); margin-top: 3px; }

.stage-readout {
  position: absolute;
  left: 18px; bottom: 16px;
  background: rgba(255,255,255,.86);
  backdrop-filter: blur(4px);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 8px 14px;
  text-align: left;
}
.big-num { font-size: 22px; font-weight: 800; color: var(--accent); line-height: 1.2; }
.sub-num { font-size: 13px; color: var(--muted); }

.axis { margin-top: 18px; padding: 0 4px; }
.axis-track {
  position: relative;
  height: 8px;
  border-radius: 999px;
  background: linear-gradient(90deg, var(--u-mm), var(--u-cm), var(--u-dm), var(--u-m), var(--u-km));
  opacity: .85;
}
.axis-dot {
  position: absolute; top: 50%; left: 0;
  width: 18px; height: 18px;
  border-radius: 50%;
  background: #fff;
  border: 3px solid var(--accent);
  transform: translate(-50%, -50%);
  transition: left .55s cubic-bezier(.34,1.3,.5,1);
  box-shadow: 0 2px 6px rgba(16,24,40,.2);
}
.axis-ticks {
  position: relative;
  height: 36px;
  margin-top: 12px;
  font-size: 11.5px;
  color: var(--muted);
}
.axis-ticks span {
  position: absolute;
  top: 0;
  transform: translateX(-50%);
  text-align: center;
  white-space: nowrap;
}
.axis-ticks span::before {
  content: "";
  display: block;
  width: 1px; height: 7px;
  background: var(--border);
  margin: 0 auto 3px;
}
.axis-ticks span.cur { color: var(--accent); font-weight: 700; }

.theater-ctrl {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-top: 16px;
  flex-wrap: wrap;
}
.stage-pos { margin-left: auto; font-size: 13px; color: var(--muted); font-variant-numeric: tabular-nums; }

/* ④ 1 米尺 */
.ruler-wrap { overflow-x: auto; padding-bottom: 6px; }
.ruler {
  display: flex;
  gap: 3px;
  min-width: 520px;
  margin-bottom: 14px;
}
.r-block {
  flex: 1 1 0;
  height: 56px;
  border-radius: 8px;
  background: color-mix(in srgb, var(--u-dm) 22%, #fff);
  border: 1px solid color-mix(in srgb, var(--u-dm) 40%, #fff);
  display: flex; flex-direction: column;
  align-items: center; justify-content: center;
  cursor: pointer;
  font-size: 13px; font-weight: 700; color: #0f5132;
  transition: transform .12s, background .2s, box-shadow .2s;
}
.r-block:hover { transform: translateY(-2px); box-shadow: 0 6px 14px rgba(16,24,40,.1); }
.r-block .sub { font-size: 11px; font-weight: 500; color: var(--muted); }
.r-block.leaf { background: color-mix(in srgb, var(--u-mm) 18%, #fff); border-color: color-mix(in srgb, var(--u-mm) 38%, #fff); color: #9a3412; }

.zoom-panel { min-height: 120px; }
.zoom-line {
  font-size: 14.5px;
  margin-bottom: 12px;
  color: var(--text);
}
.zoom-line b { color: var(--u-m); }
.zoom-grid { display: flex; flex-wrap: wrap; gap: 5px; }
.zoom-cell {
  min-width: 40px;
  height: 40px;
  padding: 0 8px;
  border-radius: 8px;
  display: flex; align-items: center; justify-content: center;
  font-size: 12px; font-weight: 600;
  background: color-mix(in srgb, var(--u-dm) 14%, #fff);
  border: 1px solid color-mix(in srgb, var(--u-dm) 34%, #fff);
  color: #0f5132;
  animation: popIn .25s ease-out;
}
.zoom-cell.mm { background: color-mix(in srgb, var(--u-mm) 12%, #fff); border-color: color-mix(in srgb, var(--u-mm) 32%, #fff); color: #9a3412; }
.zoom-cell.pick { cursor: pointer; }
.zoom-cell.pick:hover { box-shadow: 0 0 0 3px rgba(37,99,235,.18); }
@keyframes popIn { from { opacity: 0; transform: scale(.8); } to { opacity: 1; transform: none; } }
.zoom-hint { font-size: 12.5px; color: var(--muted); margin-top: 10px; }

/* ⑤ 换算 */
.convert-ctrl { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; margin-bottom: 16px; }
.convert-ctrl input[type="number"] {
  width: 110px; padding: 9px 12px;
  border: 1px solid var(--border); border-radius: 9px;
  font-size: 15px; font-family: inherit;
}
.convert-ctrl select {
  padding: 9px 12px;
  border: 1px solid var(--border); border-radius: 9px;
  font-size: 15px; font-family: inherit; background: #fff;
}
.convert-out { display: grid; grid-template-columns: repeat(auto-fill, minmax(180px, 1fr)); gap: 12px; }
.conv-card {
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 14px 16px;
  background: #fff;
  border-left: 5px solid var(--uc);
}
.conv-card .cv-unit { font-size: 13px; color: var(--muted); font-weight: 600; }
.conv-card .cv-val {
  font-size: 26px; font-weight: 800; color: var(--uc);
  line-height: 1.2; margin-top: 2px;
  font-variant-numeric: tabular-nums;
  transition: color .2s;
}
.conv-card .cv-val.bump { animation: bump .35s ease; }
@keyframes bump { 0% { transform: scale(1); } 40% { transform: scale(1.12); } 100% { transform: scale(1); } }
.conv-card .cv-bar { height: 6px; border-radius: 999px; background: #eef2f7; margin-top: 10px; overflow: hidden; }
.conv-card .cv-bar > i { display: block; height: 100%; border-radius: 999px; background: var(--uc); width: 0; transition: width .7s cubic-bezier(.22,.61,.36,1); }

/* ⑥ 小测验 */
.quiz { display: flex; flex-direction: column; gap: 16px; }
.q-item {
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 16px 18px;
  background: #fff;
}
.q-item.done-ok { border-color: #bbf7d0; background: var(--ok-soft); }
.q-item.done-bad { border-color: #fecaca; background: var(--bad-soft); }
.q-text { font-size: 15.5px; font-weight: 600; margin-bottom: 12px; }
.q-text .q-num { color: var(--accent); margin-right: 6px; }
.q-opts { display: flex; flex-wrap: wrap; gap: 10px; }
.q-opt {
  border: 1px solid var(--border);
  background: #fff;
  border-radius: 10px;
  padding: 9px 16px;
  font-size: 14.5px;
  font-family: inherit;
  cursor: pointer;
  transition: background .12s, border-color .12s, transform .05s;
}
.q-opt:hover:not(:disabled) { border-color: var(--accent); background: var(--accent-soft); }
.q-opt:active:not(:disabled) { transform: translateY(1px); }
.q-opt:disabled { cursor: default; }
.q-opt.correct { background: var(--ok); border-color: var(--ok); color: #fff; font-weight: 600; }
.q-opt.wrong { background: var(--bad); border-color: var(--bad); color: #fff; font-weight: 600; }
.q-feed { font-size: 13.5px; margin-top: 10px; min-height: 0; }
.q-feed.ok { color: #15803d; }
.q-feed.bad { color: #b91c1c; }
.q-feed:empty { display: none; }

.quiz-foot { display: flex; align-items: center; gap: 16px; margin-top: 16px; }
.quiz-score { font-size: 14px; color: var(--muted); }

@media (max-width: 640px) {
  .wrap { padding: 20px 14px 56px; }
  .theater .stage3d { height: 320px; }
  .human { font-size: 42px; }
  .convert-out { grid-template-columns: 1fr 1fr; }
}

@media (prefers-reduced-motion: reduce) {
  .obj { animation: none; }
  .scene, .axis-dot, .lad-fill, .cv-bar > i { transition: none; }
}