@font-face {
  font-family: "Ouyang Xun";
  src: url("../../assets/font/正欧阳询楷书+简繁.TTF") format("truetype");
  font-display: swap;
}

:root {
  --paper: #f2eee6;
  --paper-deep: #e6dece;
  --paper-soft: #fbf8f2;
  --ink: #1f221f;
  --ink-soft: #4f554f;
  --night: #0f1722;
  --night-deep: #0a1018;
  --copper: #a46c3b;
  --copper-soft: #d0a165;
  --cinnabar: #98372f;
  --jade: #466a63;
  --line: rgba(31, 34, 31, 0.16);
  --line-light: rgba(255, 255, 255, 0.18);
  --serif: "Ouyang Xun", "STKaiti", "KaiTi", "Noto Serif SC", serif;
  --body: "Songti SC", "STSong", "Source Han Serif SC", serif;
  --sans: "Hiragino Sans GB", "PingFang SC", "Microsoft YaHei", sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: var(--body);
}
body::selection {
  color: #fff7ec;
  background: var(--cinnabar);
}
a { color: inherit; }
button, input { font: inherit; }

.paper-grain {
  position: fixed;
  inset: 0;
  z-index: 20;
  pointer-events: none;
  opacity: 0.12;
  background-image:
    repeating-linear-gradient(0deg, transparent 0 4px, rgba(31,34,31,0.03) 4px 5px),
    repeating-linear-gradient(90deg, transparent 0 7px, rgba(152,55,47,0.02) 7px 8px),
    radial-gradient(circle at 17% 21%, rgba(31,34,31,0.09) 0 0.6px, transparent 1px),
    radial-gradient(circle at 73% 61%, rgba(164,108,59,0.11) 0 0.7px, transparent 1.2px);
  background-size: auto, auto, 10px 11px, 13px 15px;
  mix-blend-mode: multiply;
}

.progress-bar {
  position: fixed;
  top: 0;
  left: 0;
  z-index: 30;
  width: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--cinnabar), var(--copper-soft));
}

.masthead {
  position: sticky;
  top: 0;
  z-index: 15;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  min-height: 4.8rem;
  padding: 0 3vw;
  border-bottom: 1px solid rgba(255,255,255,0.08);
  color: #efe8db;
  background: rgba(15,23,34,0.88);
  backdrop-filter: blur(14px);
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.75rem;
  width: max-content;
  text-decoration: none;
  letter-spacing: 0.14em;
  font-size: 0.8rem;
}
.brand-seal {
  display: grid;
  place-items: center;
  width: 2rem;
  height: 2rem;
  border: 1px solid rgba(208,161,101,0.75);
  color: #f7d79c;
  font-family: var(--serif);
  font-size: 1.12rem;
  transform: rotate(-4deg);
}
.masthead nav {
  display: flex;
  gap: 1.45rem;
  font-size: 0.72rem;
  letter-spacing: 0.16em;
}
.masthead nav a,
.home-link {
  color: #b4bdc0;
  text-decoration: none;
  transition: color 0.2s ease, opacity 0.2s ease;
}
.masthead nav a:hover,
.masthead nav a:focus-visible,
.home-link:hover,
.home-link:focus-visible {
  color: #f1d49d;
}
.home-link {
  justify-self: end;
  font-size: 0.72rem;
}

main { overflow: hidden; }

.hero {
  min-height: calc(100vh - 4.8rem);
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(22rem, 0.95fr) 9rem;
  align-items: center;
  gap: 4vw;
  padding: 7vh 6vw;
  color: #f3efe6;
  background:
    radial-gradient(circle at 74% 36%, rgba(52,88,98,0.7) 0, rgba(15,23,34,0.12) 32%, transparent 48%),
    radial-gradient(circle at 18% 78%, rgba(152,55,47,0.18), transparent 32%),
    linear-gradient(160deg, #101823 0%, #121d2a 50%, #0b1018 100%);
}
.eyebrow,
.chapter-no,
.topics-head p,
.sources > div > p {
  margin: 0 0 1.2rem;
  color: #c4876f;
  font-family: var(--sans);
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.24em;
  text-transform: uppercase;
}
.hero h1 {
  margin: 0;
  font-family: var(--serif);
  font-size: clamp(3rem, 5.8vw, 6rem);
  font-weight: 400;
  line-height: 1.02;
}
.hero h1 em {
  color: #f0ca86;
  font-style: normal;
}
.lead {
  max-width: 38rem;
  margin: 1.5rem 0 2rem;
  color: #c1ccd0;
  font-size: clamp(1rem, 1.18vw, 1.16rem);
  line-height: 1.92;
}
.hero-claim {
  display: inline-grid;
  gap: 0.35rem;
  margin-bottom: 2rem;
  padding: 0.95rem 1rem;
  border: 1px solid rgba(255,255,255,0.12);
  background: rgba(255,255,255,0.04);
}
.hero-claim span {
  color: #8fa1ab;
  font-size: 0.64rem;
  letter-spacing: 0.18em;
}
.hero-claim strong {
  color: #f4d394;
  font-family: var(--serif);
  font-size: 1.6rem;
  font-weight: 400;
}
.hero-claim p {
  margin: 0;
  color: #c4cdd0;
  font-size: 0.84rem;
  line-height: 1.8;
}
.start-link {
  display: inline-flex;
  align-items: center;
  gap: 1.25rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid rgba(241,212,157,0.48);
  color: #f1d49d;
  text-decoration: none;
  font-size: 0.8rem;
  letter-spacing: 0.16em;
}
.start-link i { font-style: normal; }

.hero-orbit {
  position: relative;
  aspect-ratio: 1;
  max-width: 36rem;
}
.sphere {
  position: absolute;
  border: 1px solid rgba(241,212,157,0.22);
  border-radius: 50%;
}
.sphere-outer { inset: 4%; }
.sphere-mid { inset: 18%; }
.sphere-inner { inset: 34%; }
.hero-core {
  position: absolute;
  inset: 39%;
  display: grid;
  place-items: center;
  align-content: center;
  border-radius: 50%;
  color: #1d231f;
  background: radial-gradient(circle at 35% 30%, #f4ddae, #d5a456 65%, #8c5e29);
  box-shadow: 0 0 3.5rem rgba(208,161,101,0.22);
}
.hero-core span,
.hero-core i {
  color: #664114;
  font-size: 0.65rem;
  letter-spacing: 0.14em;
}
.hero-core b {
  font-family: var(--serif);
  font-size: clamp(2.2rem, 4vw, 4rem);
  font-weight: 400;
  line-height: 1;
}
.dipper {
  position: absolute;
  inset: 0;
  animation: orbit-turn 22s linear infinite;
}
.star {
  position: absolute;
  width: 0.56rem;
  height: 0.56rem;
  border-radius: 50%;
  background: #f7e4bc;
  box-shadow: 0 0 1rem rgba(255,231,190,0.8);
}
.star-1 { top: 27%; left: 63%; }
.star-2 { top: 39%; left: 69%; }
.star-3 { top: 45%; left: 58%; }
.star-4 { top: 35%; left: 52%; }
.star-5 { top: 29%; left: 42%; }
.star-6 { top: 24%; left: 32%; }
.star-7 { top: 28%; left: 21%; }
.quadrant {
  position: absolute;
  color: #8da2ac;
  font-size: 0.72rem;
  letter-spacing: 0.2em;
}
.q-east { left: 7%; top: 44%; }
.q-south { bottom: 7%; left: 44%; }
.q-west { right: 7%; top: 44%; }
.q-north { top: 7%; left: 44%; }
.hero-aside {
  display: grid;
  gap: 0.32rem;
  padding-left: 1.5rem;
  border-left: 1px solid rgba(255,255,255,0.14);
}
.hero-aside span {
  margin-top: 0.78rem;
  color: #778994;
  font-family: var(--sans);
  font-size: 0.66rem;
  letter-spacing: 0.12em;
}
.hero-aside b {
  font-size: 0.84rem;
  font-weight: 400;
}

@keyframes orbit-turn {
  to { transform: rotate(360deg); }
}

.thesis-strip {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 2rem;
  padding: 1.1rem 5vw;
  color: #b7c2c2;
  background: #1a2730;
}
.thesis-strip strong {
  color: #f1ddaf;
  font-family: var(--serif);
  font-size: clamp(1.1rem, 2vw, 2rem);
  font-weight: 400;
  text-align: center;
}
.thesis-strip span {
  font-size: 0.72rem;
  letter-spacing: 0.16em;
}
.thesis-strip span:last-child { text-align: right; }

.chapter,
.topics,
.sources {
  padding: clamp(4.8rem, 8vw, 8rem) 6vw;
}
.chapter {
  display: grid;
  grid-template-columns: minmax(16rem, 0.58fr) minmax(0, 1.42fr);
  gap: 5vw;
}
.chapter-intro {
  align-self: start;
  position: sticky;
  top: 6.5rem;
}
.chapter-intro h2,
.topics-head h2,
.sources h2 {
  margin: 0;
  font-family: var(--serif);
  font-size: clamp(2.3rem, 4.5vw, 4.8rem);
  font-weight: 400;
  line-height: 1.16;
}
.chapter-intro h2 em,
.topics-head h2 em {
  color: var(--cinnabar);
  font-style: normal;
}
.chapter-intro > p:not(.chapter-no) {
  max-width: 32rem;
  font-size: 0.98rem;
  line-height: 1.95;
}

.stage {
  align-self: center;
  min-width: 0;
  padding: clamp(1.5rem, 4vw, 3rem);
  border: 1px solid var(--line);
}

.chapter-night {
  color: #edf0e9;
  background: var(--night);
}
.chapter-night .chapter-intro h2 em,
.chapter-dark-copper .chapter-intro h2 em {
  color: #f0d08b;
}
.chapter-night .chapter-intro > p,
.chapter-dark-copper .chapter-intro > p {
  color: #a9b6bc;
}
.chapter-night .stage,
.chapter-dark-copper .stage {
  border-color: rgba(255,255,255,0.14);
  background: rgba(255,255,255,0.04);
}

.chapter-paper {
  background: var(--paper);
}
.chapter-paper .chapter-intro > p,
.chapter-earth .chapter-intro > p,
.chapter-evolution .chapter-intro > p,
.sources > div > p:last-child {
  color: var(--ink-soft);
}

.chapter-earth {
  background: #e3dfd1;
}

.chapter-dark-copper {
  color: #f4ede3;
  background: linear-gradient(180deg, #30261f 0, #1b1916 100%);
}

.chapter-evolution {
  background: #efe8db;
}

.timeline {
  --range-color: var(--cinnabar);
  appearance: none;
  width: 100%;
  height: 2.6rem;
  margin: 0;
  background: transparent;
}
.timeline::-webkit-slider-runnable-track {
  height: 4px;
  border-radius: 99px;
  background: color-mix(in srgb, var(--range-color) 35%, transparent);
}
.timeline::-webkit-slider-thumb {
  appearance: none;
  width: 2rem;
  height: 2rem;
  margin-top: calc((4px - 2rem) / 2);
  border: 2px solid color-mix(in srgb, var(--range-color) 80%, white);
  border-radius: 50%;
  background: var(--paper-soft);
  box-shadow: 0 0 0 0.45rem color-mix(in srgb, var(--range-color) 16%, transparent);
}
.timeline::-moz-range-track {
  height: 4px;
  border: 0;
  border-radius: 99px;
  background: color-mix(in srgb, var(--range-color) 35%, transparent);
}
.timeline::-moz-range-thumb {
  width: 2rem;
  height: 2rem;
  border: 2px solid color-mix(in srgb, var(--range-color) 80%, white);
  border-radius: 50%;
  background: var(--paper-soft);
  box-shadow: 0 0 0 0.45rem color-mix(in srgb, var(--range-color) 16%, transparent);
}
.timeline-copper { --range-color: var(--copper); }
.timeline-gold { --range-color: var(--copper-soft); }
.timeline-label {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 0.8rem;
  margin: 1.8rem 0 0.4rem;
  font-family: var(--sans);
  font-size: 0.7rem;
  letter-spacing: 0.08em;
}
.timeline-label b {
  font-weight: 400;
  text-align: center;
}
.timeline-label span:last-child { text-align: right; }

.stage-why {
  display: grid;
  grid-template-columns: 1fr minmax(22rem, 0.9fr);
  gap: 2rem;
}
.reason-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1px;
  background: rgba(255,255,255,0.12);
}
.reason-grid article {
  min-height: 12rem;
  padding: 1.5rem;
  background: rgba(22,34,48,0.82);
}
.reason-grid article:last-child {
  grid-column: 1 / -1;
}
.reason-grid span {
  color: #f0d08b;
  font-size: 0.72rem;
  letter-spacing: 0.16em;
}
.reason-grid b {
  display: block;
  margin: 0.8rem 0 0.9rem;
  font-family: var(--serif);
  font-size: 1.45rem;
  font-weight: 400;
  line-height: 1.45;
}
.reason-grid p {
  margin: 0;
  color: #adb8be;
  line-height: 1.82;
}
.sky-clock {
  padding: 1.5rem;
  border: 1px solid rgba(255,255,255,0.14);
  background: rgba(10,18,27,0.55);
}
.clock-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
}
.clock-head span {
  color: #87949d;
  font-size: 0.72rem;
  letter-spacing: 0.16em;
}
.clock-head strong {
  color: #f1ddaf;
  font-family: var(--serif);
  font-size: 1.15rem;
  font-weight: 400;
}
.clock-stage {
  position: relative;
  aspect-ratio: 1;
  margin: 1.5rem 0;
  border-radius: 50%;
  border: 1px solid rgba(255,255,255,0.18);
}
.clock-stage::before,
.clock-stage::after {
  content: "";
  position: absolute;
  inset: 14%;
  border: 1px solid rgba(255,255,255,0.1);
  border-radius: 50%;
}
.clock-stage::after {
  inset: 32%;
}
.polar-core {
  position: absolute;
  inset: 39%;
  display: grid;
  place-items: center;
  align-content: center;
  border-radius: 50%;
  color: #edf1e8;
  background: rgba(241,221,175,0.12);
  border: 1px solid rgba(241,221,175,0.28);
}
.polar-core i,
.polar-core b {
  font-style: normal;
  font-weight: 400;
}
.polar-core i {
  font-size: 0.68rem;
  color: #c3cfcc;
}
.polar-core b {
  font-family: var(--serif);
  font-size: 1.35rem;
}
.dipper-ring {
  position: absolute;
  inset: 0;
  transition: transform 0.4s ease;
}
.dipper-ring span {
  position: absolute;
  width: 0.58rem;
  height: 0.58rem;
  border-radius: 50%;
  background: #f4dfba;
  box-shadow: 0 0 0.9rem rgba(255,230,189,0.55);
}
.dipper-ring .s1 { top: 26%; left: 65%; }
.dipper-ring .s2 { top: 38%; left: 71%; }
.dipper-ring .s3 { top: 44%; left: 60%; }
.dipper-ring .s4 { top: 34%; left: 54%; }
.dipper-ring .s5 { top: 28%; left: 43%; }
.dipper-ring .s6 { top: 24%; left: 33%; }
.dipper-ring .s7 { top: 28%; left: 22%; }
.season-label {
  position: absolute;
  color: #7c8b93;
  font-size: 0.7rem;
  letter-spacing: 0.16em;
}
.season-east { left: 8%; top: 46%; }
.season-south { left: 47%; bottom: 8%; }
.season-west { right: 8%; top: 46%; }
.season-north { left: 47%; top: 8%; }
.stage-why .timeline-label { color: #8b98a0; }
.stage-why .timeline-label b { color: #f0ece1; }

.stage-cosmos {
  display: grid;
  gap: 1.4rem;
}
.mode-tabs,
.instrument-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
}
.mode-tab,
.instrument-tab,
.evolution-node {
  appearance: none;
  padding: 0.72rem 1rem;
  border: 1px solid var(--line);
  color: var(--ink-soft);
  background: rgba(255,255,255,0.45);
  cursor: pointer;
  font-family: var(--body);
  transition: color 0.2s ease, background 0.2s ease, transform 0.2s ease;
}
.mode-tab:hover,
.instrument-tab:hover,
.evolution-node:hover,
.mode-tab.is-active,
.instrument-tab.is-active,
.evolution-node.is-active {
  color: #fff8ec;
  background: var(--cinnabar);
  transform: translateY(-2px);
}
.cosmos-grid,
.instrument-grid {
  display: grid;
  grid-template-columns: minmax(18rem, 0.95fr) minmax(18rem, 1.05fr);
  gap: 2rem;
}
.cosmos-visual {
  position: relative;
  aspect-ratio: 1;
  overflow: hidden;
  border: 1px solid var(--line);
  background:
    radial-gradient(circle at 50% 30%, rgba(70,106,99,0.18), transparent 35%),
    radial-gradient(circle at 55% 56%, rgba(164,108,59,0.12), transparent 28%),
    linear-gradient(180deg, #f6f1e6 0, #ebe3d3 100%);
}
.cosmos-shell,
.cosmos-earth,
.cosmos-sun {
  position: absolute;
  transition: all 0.35s ease;
}
.cosmos-shell {
  left: 10%;
  right: 10%;
  top: 14%;
  bottom: 14%;
  border: 2px solid rgba(70,106,99,0.6);
  border-radius: 50%;
}
.cosmos-earth {
  left: 37%;
  right: 37%;
  top: 37%;
  bottom: 37%;
  border-radius: 50%;
  background: radial-gradient(circle at 35% 30%, #658d7a, #365b52 70%);
}
.cosmos-sun {
  top: 46%;
  left: 74%;
  display: grid;
  width: 2.8rem;
  height: 2.8rem;
  place-items: center;
  border-radius: 50%;
  color: #6a4318;
  background: radial-gradient(circle at 35% 30%, #ffe5a6, #dd9c3b 70%, #af6a1f);
  transform: translate(-50%, -50%);
}
.visual-label {
  position: absolute;
  color: #6e736e;
  font-size: 0.72rem;
  letter-spacing: 0.12em;
}
.visual-label.top { top: 1rem; left: 50%; transform: translateX(-50%); }
.visual-label.bottom { bottom: 1rem; left: 50%; transform: translateX(-50%); }
.cosmos-copy span {
  color: var(--cinnabar);
  font-size: 0.72rem;
  letter-spacing: 0.16em;
}
.cosmos-copy h3,
.earth-reading h3,
.instrument-copy h3,
.evolution-panel h3,
.topic-card h3 {
  margin: 0.7rem 0 1rem;
  font-family: var(--serif);
  font-size: 2rem;
  font-weight: 400;
}
.cosmos-copy p,
.earth-reading p,
.measure-reading p,
.instrument-copy p,
.evolution-panel p,
.topic-card p {
  margin: 0;
  line-height: 1.88;
}
.cosmos-copy blockquote {
  margin: 1.35rem 0;
  padding: 1rem 1rem 1rem 1.2rem;
  border-left: 3px solid var(--cinnabar);
  color: #444b44;
  background: rgba(255,255,255,0.44);
  font-family: var(--serif);
  font-size: 1.15rem;
}
.cosmos-copy cite {
  display: block;
  margin-top: 0.5rem;
  color: #7a7d74;
  font-size: 0.72rem;
  font-style: normal;
}
.people-strip,
.instrument-points,
.modern-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
  margin: 1.2rem 0;
}
.people-strip span,
.instrument-points span,
.modern-grid span {
  padding: 0.45rem 0.65rem;
  border: 1px solid var(--line);
  color: var(--ink-soft);
  font-size: 0.72rem;
}
.conclusion {
  margin-top: 1rem;
  padding-top: 1rem;
  border-top: 1px solid var(--line);
  color: var(--cinnabar);
}

.stage-earth {
  display: grid;
  grid-template-columns: minmax(18rem, 0.92fr) minmax(18rem, 1.08fr);
  gap: 2rem;
}
.earth-stage {
  display: grid;
  place-items: center;
  min-height: 28rem;
  border: 1px solid rgba(31,34,31,0.12);
  background: linear-gradient(180deg, #cfd9d9 0, #e4dfd1 58%, #d5c9b8 100%);
}
.earth-shell {
  position: relative;
  width: min(28rem, 85%);
  aspect-ratio: 1;
}
.earth-floor {
  position: absolute;
  left: 8%;
  right: 8%;
  bottom: 22%;
  height: 1rem;
  border-radius: 999px;
  background: #6d7e62;
  transition: all 0.35s ease;
}
.earth-horizon {
  position: absolute;
  left: 10%;
  right: 10%;
  top: 18%;
  bottom: 15%;
  border: 1px dashed rgba(31,34,31,0.18);
  border-radius: 50%;
}
.earth-caption {
  position: absolute;
  right: 0;
  left: 0;
  bottom: 2%;
  color: #59615a;
  font-size: 0.78rem;
  text-align: center;
}
.earth-reading {
  display: flex;
  flex-direction: column;
  justify-content: center;
}
.earth-reading span,
.measure-head span,
.instrument-copy span,
.evolution-panel span {
  color: var(--cinnabar);
  font-size: 0.72rem;
  letter-spacing: 0.16em;
}
.earth-notes {
  display: grid;
  gap: 0.8rem;
  margin-top: 1.4rem;
}
.earth-notes p {
  margin: 0;
  padding: 0.9rem 1rem;
  border: 1px solid rgba(31,34,31,0.12);
  background: rgba(255,255,255,0.36);
}

.stage-measure {
  display: grid;
  grid-template-columns: minmax(21rem, 1fr) minmax(18rem, 0.92fr);
  gap: 2rem;
}
.measure-visual {
  display: grid;
  grid-template-columns: minmax(0, 0.9fr) minmax(0, 1.1fr);
  gap: 1.2rem;
}
.sundial,
.meridian {
  position: relative;
  min-height: 28rem;
  border: 1px solid rgba(255,255,255,0.12);
  background: rgba(255,255,255,0.04);
}
.sundial::after {
  content: "";
  position: absolute;
  right: 10%;
  left: 10%;
  bottom: 18%;
  border-top: 2px solid rgba(255,255,255,0.22);
}
.gnomon {
  position: absolute;
  left: 50%;
  bottom: 18%;
  width: 6px;
  height: 46%;
  background: #ebd7b3;
  transform: translateX(-50%);
}
.shadow {
  position: absolute;
  left: calc(50% + 3px);
  bottom: 18%;
  width: 32%;
  height: 2px;
  background: #c58b55;
  transform-origin: left center;
  transition: width 0.3s ease, transform 0.3s ease;
}
.ground-scale {
  position: absolute;
  right: 10%;
  left: 10%;
  bottom: 8%;
  display: flex;
  align-items: baseline;
  justify-content: space-between;
}
.ground-scale span {
  color: #b6c0c1;
  font-size: 0.72rem;
  letter-spacing: 0.14em;
}
.ground-scale b {
  color: #f1d49d;
  font-family: var(--serif);
  font-weight: 400;
}
.meridian {
  padding: 1.3rem;
}
.station {
  position: absolute;
  left: 50%;
  width: 8rem;
  margin-left: -4rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.4rem;
  text-align: center;
}
.station span {
  color: #b9c3c7;
  font-size: 0.72rem;
  letter-spacing: 0.14em;
}
.station b {
  font-family: var(--serif);
  font-size: 1.4rem;
  font-weight: 400;
}
.station-north { top: 8%; }
.station-south { bottom: 8%; }
.meridian-line {
  position: absolute;
  top: 20%;
  bottom: 20%;
  left: 50%;
  width: 2px;
  background: linear-gradient(180deg, #d0a165, rgba(208,161,101,0.22));
  transform: translateX(-50%);
}
.arc-note {
  position: absolute;
  top: 50%;
  right: 8%;
  color: #f1d49d;
  font-size: 0.8rem;
  transform: translateY(-50%);
}
.measure-reading {
  display: flex;
  flex-direction: column;
  justify-content: center;
}
.measure-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
}
.measure-head strong {
  font-family: var(--serif);
  font-size: 1.15rem;
  font-weight: 400;
}
.measure-facts {
  display: grid;
  gap: 0.8rem;
  margin-top: 1.2rem;
}
.measure-facts p {
  margin: 0;
  padding: 0.9rem 1rem;
  border: 1px solid rgba(255,255,255,0.12);
  background: rgba(255,255,255,0.04);
}

.stage-instruments {
  display: grid;
  gap: 1.2rem;
}
.instrument-visual {
  position: relative;
  min-height: 32rem;
  overflow: hidden;
  border: 1px solid var(--line);
  background:
    radial-gradient(circle at 50% 50%, rgba(208,161,101,0.12), transparent 26%),
    linear-gradient(180deg, #f6f1e7, #e5dbc7);
}
.ring {
  position: absolute;
  border: 2px solid rgba(164,108,59,0.78);
  border-radius: 50%;
  transition: all 0.35s ease;
}
.ring-a {
  inset: 13%;
  animation: slow-spin 20s linear infinite;
}
.ring-b {
  inset: 24%;
  animation: slow-spin-reverse 16s linear infinite;
}
.ring-c {
  inset: 35%;
  animation: slow-spin 12s linear infinite;
}
.instrument-core {
  position: absolute;
  inset: 42%;
  display: grid;
  place-items: center;
  border-radius: 50%;
  color: #f8efe0;
  background: linear-gradient(180deg, #b8834d, #7f4d22);
  font-family: var(--serif);
  font-size: 2rem;
}
.instrument-extra {
  position: absolute;
  right: 1rem;
  bottom: 1rem;
  padding: 0.5rem 0.8rem;
  border: 1px solid rgba(31,34,31,0.16);
  color: var(--ink-soft);
  background: rgba(255,255,255,0.44);
  font-size: 0.76rem;
}
.instrument-copy {
  display: flex;
  flex-direction: column;
  justify-content: center;
}

@keyframes slow-spin {
  to { transform: rotate(360deg); }
}
@keyframes slow-spin-reverse {
  to { transform: rotate(-360deg); }
}

.stage-evolution {
  display: grid;
  gap: 1.4rem;
}
.evolution-track {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
}
.evolution-panel {
  padding: 1.5rem;
  border: 1px solid var(--line);
  background: rgba(255,255,255,0.42);
}

.topics {
  background: #f5f1e8;
}
.topics-head {
  margin-bottom: 2.2rem;
}
.topic-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1px;
  background: var(--line);
}
.topic-card {
  min-height: 14rem;
  padding: 1.5rem;
  background: #fffdf8;
}
.topic-card span {
  color: var(--cinnabar);
  font-size: 0.72rem;
  letter-spacing: 0.16em;
}

.sources {
  display: grid;
  grid-template-columns: minmax(16rem, 0.7fr) minmax(0, 1.3fr);
  gap: 5vw;
  background: #ded3c0;
}
.sources ol {
  margin: 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid rgba(31,34,31,0.18);
}
.sources li {
  display: grid;
  grid-template-columns: 4rem 1fr;
  gap: 1rem;
  border-bottom: 1px solid rgba(31,34,31,0.18);
}
.sources li span {
  padding: 1rem 0;
  color: var(--cinnabar);
  font-size: 0.68rem;
  letter-spacing: 0.16em;
}
.sources a {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1rem 0;
  text-decoration: none;
  font-family: var(--body);
  font-size: 1rem;
}
.sources a:hover { color: var(--cinnabar); }
.sources a i {
  font-style: normal;
}

footer {
  display: flex;
  min-height: 9rem;
  align-items: center;
  justify-content: space-between;
  gap: 2rem;
  padding: 2.2rem 6vw;
  color: #eadfcd;
  background: #161a18;
}
footer p {
  margin: 0 0 0.35rem;
  font-family: var(--serif);
  font-size: 1.6rem;
}
footer span {
  color: #aab5ae;
  font-size: 0.82rem;
}
footer a {
  color: #f1d49d;
  text-decoration: none;
  border-bottom: 1px solid rgba(241,212,157,0.5);
  padding-bottom: 0.4rem;
}

@media (max-width: 1100px) {
  .hero {
    grid-template-columns: 1fr 1fr;
  }
  .hero-aside {
    display: none;
  }
  .chapter,
  .sources {
    grid-template-columns: 1fr;
  }
  .chapter-intro {
    position: static;
  }
  .stage-why,
  .cosmos-grid,
  .stage-earth,
  .stage-measure,
  .instrument-grid {
    grid-template-columns: 1fr;
  }
  .topic-grid {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 760px) {
  .masthead {
    grid-template-columns: 1fr auto;
    padding: 0 1rem;
  }
  .masthead nav,
  .home-link {
    display: none;
  }
  .hero {
    min-height: auto;
    grid-template-columns: 1fr;
    padding: 5rem 1.2rem 4rem;
  }
  .thesis-strip {
    grid-template-columns: 1fr;
    text-align: center;
  }
  .thesis-strip span:last-child {
    text-align: center;
  }
  .chapter,
  .topics,
  .sources {
    padding: 4.5rem 1.2rem;
  }
  .stage {
    padding: 1.2rem;
  }
  .reason-grid,
  .measure-visual,
  .topic-grid {
    grid-template-columns: 1fr;
  }
  .reason-grid article:last-child {
    grid-column: auto;
  }
  .mode-tabs,
  .instrument-tabs,
  .evolution-track {
    display: grid;
    grid-template-columns: 1fr 1fr;
  }
  .timeline-label {
    grid-template-columns: 1fr;
    text-align: center;
  }
  .timeline-label span:last-child {
    text-align: center;
  }
  .sources li {
    grid-template-columns: 3rem 1fr;
  }
  footer {
    align-items: flex-start;
    flex-direction: column;
  }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation: none !important;
    transition: none !important;
  }
}