/* Shared lesson design system for physiology/anatomy chapters.
   Reuse this file across chapter pages before adding chapter-specific styles. */
:root {
  --ink: #17202a;
  --text: #334155;
  --muted: #667085;
  --line: #d9e2ec;
  --paper: #f5f7fa;
  --panel: #ffffff;
  --blue: #1d4ed8;
  --teal: #0f766e;
  --green: #15803d;
  --amber: #b45309;
  --red: #b91c1c;
  --violet: #6d28d9;
  --shadow: 0 14px 32px rgba(15, 23, 42, .10);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  color: var(--ink);
  background: linear-gradient(180deg, #eef6f7 0, #f8fafc 42%, #f4f7f2 100%);
  letter-spacing: 0;
}
button, input { font: inherit; }
button { cursor: pointer; }
header {
  position: sticky;
  top: 0;
  z-index: 10;
  border-bottom: 1px solid var(--line);
  background: rgba(248, 250, 252, .95);
  backdrop-filter: blur(10px);
}
.topbar {
  max-width: 1240px;
  margin: 0 auto;
  padding: 14px 18px;
  display: grid;
  grid-template-columns: minmax(260px, 1fr) auto;
  gap: 14px;
  align-items: center;
}
h1 {
  margin: 0;
  font-size: clamp(1.12rem, 2.4vw, 1.85rem);
  line-height: 1.08;
  letter-spacing: 0;
}
.subtitle { margin: 5px 0 0; color: var(--muted); font-size: .94rem; }
nav { display: flex; flex-wrap: wrap; gap: 8px; justify-content: flex-end; }
nav a {
  color: var(--ink);
  text-decoration: none;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 8px 10px;
  font-size: .9rem;
}
main {
  max-width: 1240px;
  margin: 0 auto;
  padding: 18px;
  display: grid;
  gap: 18px;
}
section {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
  box-shadow: var(--shadow);
  overflow: hidden;
}
.section-head {
  padding: 18px 20px;
  border-bottom: 1px solid var(--line);
  background: #fbfdff;
}
.section-head h2 {
  margin: 0;
  font-size: clamp(1.25rem, 2vw, 1.65rem);
  letter-spacing: 0;
}
.section-head p { margin: 8px 0 0; color: var(--text); max-width: 86ch; line-height: 1.58; }
.body { padding: 18px 20px 20px; }
.grid { display: grid; gap: 16px; }
.cols-2 { grid-template-columns: minmax(0, 1fr) minmax(320px, .95fr); }
.cols-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.card {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  padding: 14px;
}
.card h3, .card h4 { margin: 0 0 8px; letter-spacing: 0; }
p, li { color: var(--text); line-height: 1.6; }
ul { margin: 8px 0 0 18px; padding: 0; }
.pillrow { display: flex; flex-wrap: wrap; gap: 8px; }
.pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 9px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: #fff;
  color: var(--text);
  font-size: .92rem;
}
.dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--blue);
  display: inline-block;
  flex: 0 0 auto;
}
.dot.is-ink { background: var(--ink); }
.dot.is-blue { background: var(--blue); }
.dot.is-teal { background: var(--teal); }
.dot.is-green { background: var(--green); }
.dot.is-amber { background: var(--amber); }
.dot.is-red { background: var(--red); }
.dot.is-violet { background: var(--violet); }
.dot.is-slate { background: #64748b; }
.dot.is-slate-dark { background: #475569; }
.dot.is-charcoal { background: #334155; }
.dot.is-brown { background: #7c2d12; }
.dot.is-sky { background: #60a5fa; }
.lab {
  display: grid;
  grid-template-columns: minmax(260px, 370px) minmax(0, 1fr);
  gap: 18px;
  align-items: stretch;
}
.controls { display: grid; gap: 12px; align-content: start; }
.control {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 11px;
  background: #fbfdff;
}
.control label {
  display: flex;
  justify-content: space-between;
  gap: 10px;
  font-weight: 700;
  color: var(--ink);
  font-size: .94rem;
}
.control small { display: block; color: var(--muted); margin-top: 4px; line-height: 1.4; }
input[type="range"] { width: 100%; accent-color: var(--teal); margin-top: 10px; }
.readout {
  color: var(--teal);
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}
.viz {
  min-height: 350px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: linear-gradient(180deg, #ffffff 0, #f8fbfc 100%);
  position: relative;
  overflow: hidden;
  padding: 14px;
}
.viz svg, .viz canvas { width: 100%; height: 100%; display: block; }
.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 10px;
}
.legend span {
  display: inline-flex;
  gap: 6px;
  align-items: center;
  border: 1px solid var(--line);
  padding: 5px 8px;
  border-radius: 8px;
  background: #fff;
  color: var(--text);
  font-size: .88rem;
}
.result {
  border-left: 4px solid var(--teal);
  background: #eefaf7;
  padding: 12px;
  border-radius: 8px;
  color: #134e4a;
  line-height: 1.58;
}
.metric-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 10px;
  margin-top: 10px;
}
.metric {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 10px;
  background: #fff;
}
.metric b { display: block; font-size: 1.15rem; color: var(--ink); font-variant-numeric: tabular-nums; }
.metric span { color: var(--muted); font-size: .86rem; line-height: 1.35; display: block; }
.note {
  border: 1px solid #bfd8ff;
  border-left: 5px solid var(--blue);
  background: #f0f6ff;
  border-radius: 8px;
  padding: 13px;
}
.tech {
  border: 1px solid #c7d2fe;
  border-left: 5px solid var(--violet);
  background: #f7f5ff;
  border-radius: 8px;
  padding: 14px;
}
.game {
  border: 1px solid #f3d38b;
  border-left: 5px solid var(--amber);
  background: #fff8eb;
  border-radius: 8px;
  padding: 14px;
  display: grid;
  gap: 10px;
}
.answers { display: flex; flex-wrap: wrap; gap: 8px; }
.answers button {
  border: 1px solid #e4bb63;
  background: #fff;
  border-radius: 8px;
  padding: 9px 11px;
  color: var(--ink);
}
.answers button.good { border-color: var(--green); background: #effaf1; }
.answers button.bad { border-color: var(--red); background: #fff1f2; }
.feedback { min-height: 28px; color: #713f12; line-height: 1.5; }
.timeline {
  display: grid;
  gap: 10px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #f8fafc;
  padding: 10px;
  margin-top: 10px;
}
.trace-panel {
  height: 82px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  position: relative;
  overflow: hidden;
}
.trace-title {
  position: absolute;
  left: 12px;
  top: 10px;
  color: var(--ink);
  font-weight: 700;
  font-size: .9rem;
  z-index: 2;
}
.trace-axis-note {
  position: absolute;
  right: 12px;
  bottom: 8px;
  color: var(--muted);
  font-size: .78rem;
  z-index: 2;
}
.wave {
  position: absolute;
  left: 0;
  width: 30%;
  height: 22px;
  border-top: 4px solid currentColor;
  opacity: .9;
  transform-origin: left center;
}
.wave::before {
  content: "";
  position: absolute;
  left: -5px;
  top: -9px;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: currentColor;
}
.wave::after {
  content: "";
  position: absolute;
  left: 0;
  top: -5px;
  width: 100%;
  height: 10px;
  background: repeating-linear-gradient(90deg, currentColor 0 8px, transparent 8px 24px);
  opacity: .18;
}
.time-marker {
  position: absolute;
  top: 0;
  bottom: 0;
  width: 2px;
  background: var(--ink);
}
.time-label {
  position: absolute;
  top: 8px;
  transform: translateX(-50%);
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 3px 6px;
  font-size: .78rem;
  color: var(--text);
  white-space: nowrap;
}
.time-marker.is-start,
.time-label.is-start {
  left: 50%;
}
.wave.is-tra {
  top: 48px;
  color: var(--teal);
}
.wave.is-limb {
  top: 48px;
  color: var(--blue);
}
.barbox {
  height: 18px;
  border-radius: 999px;
  background: #e2e8f0;
  overflow: hidden;
  margin-top: 7px;
}
.bar { height: 100%; width: 50%; background: var(--teal); transition: width .2s ease; }
.anatomy-wrap {
  display: grid;
  grid-template-columns: minmax(0, 1.15fr) minmax(280px, .85fr);
  gap: 16px;
  align-items: center;
}
.photo-card {
  display: grid;
  grid-template-columns: minmax(160px, 240px) minmax(0, 1fr);
  gap: 16px;
  align-items: center;
}
.photo-card img {
  width: 100%;
  max-height: 360px;
  object-fit: contain;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  padding: 8px;
}
.source {
  color: var(--muted);
  font-size: .84rem;
  line-height: 1.45;
  margin-top: 8px;
}
.concept-table {
  display: grid;
  gap: 10px;
}
.concept-row {
  display: grid;
  grid-template-columns: 190px minmax(0, 1fr);
  gap: 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 12px;
  background: #fff;
}
.concept-row b { color: var(--ink); }
.concept-row p { margin: 0; }
.svg-label { font-size: 13px; fill: #1f2937; font-weight: 700; }
.svg-small { font-size: 11px; fill: #475569; }
footer { padding: 22px; color: var(--muted); text-align: center; }
@media (max-width: 900px) {
  .topbar, .cols-2, .cols-3, .lab, .anatomy-wrap, .photo-card, .concept-row { grid-template-columns: 1fr; }
  nav { justify-content: flex-start; }
  .metric-grid { grid-template-columns: 1fr; }
  .viz { min-height: 300px; }
}