:root {
  --paper: #f7f3eb;
  --paper-deep: #ebe4d8;
  --ink: #182535;
  --muted: #66717a;
  --line: rgba(24, 37, 53, 0.13);
  --orange: #e9834f;
  --mint: #91cfc2;
  --blue: #73b8d7;
  --purple: #9c8aca;
  --card: rgba(255, 255, 255, 0.56);
  --radius: 1.35rem;
  font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
  color: var(--ink);
  background: var(--paper);
  line-height: 1.65;
  text-rendering: optimizeLegibility;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; background: var(--paper); }
body { margin: 0; min-width: 320px; overflow-x: clip; }
img { display: block; max-width: 100%; }
a { color: inherit; }
button { font: inherit; }

.skip-link { position: fixed; left: 1rem; top: -5rem; z-index: 100; padding: .6rem .8rem; background: var(--ink); color: white; border-radius: .5rem; }
.skip-link:focus { top: 1rem; }
.site-header { position: sticky; top: 0; z-index: 20; display: flex; align-items: center; justify-content: space-between; min-height: 4.1rem; padding: .7rem 1rem; background: rgba(247,243,235,.88); border-bottom: 1px solid var(--line); backdrop-filter: blur(14px); }
.brand { display: inline-flex; align-items: center; gap: .55rem; font-weight: 700; font-size: .93rem; text-decoration: none; letter-spacing: .02em; }
.brand-mark { width: .72rem; height: .72rem; border-radius: 50% 50% 50% 0; background: linear-gradient(135deg, var(--orange), var(--purple)); transform: rotate(-45deg); }
.menu-button { border: 1px solid var(--line); border-radius: 999px; color: var(--ink); background: transparent; padding: .4rem .78rem; cursor: pointer; }
.section-nav { position: absolute; right: 1rem; top: calc(100% + .5rem); display: none; width: min(17rem, calc(100vw - 2rem)); max-height: 74vh; overflow: auto; padding: .65rem; border: 1px solid var(--line); border-radius: 1rem; background: rgba(255,255,255,.97); box-shadow: 0 1.5rem 3rem rgba(24,37,53,.15); }
.section-nav.is-open { display: grid; }
.section-nav a { padding: .45rem .55rem; border-radius: .55rem; color: var(--muted); text-decoration: none; font-size: .88rem; }
.section-nav a:hover, .section-nav a:focus { color: var(--ink); background: var(--paper); }

.section-shell { width: min(100%, 78rem); margin: 0 auto; padding-inline: 1rem; }
.hero { position: relative; height: clamp(40rem, calc(91svh - 4.1rem), 47rem); min-height: clamp(40rem, calc(91svh - 4.1rem), 47rem); display: grid; align-items: stretch; isolation: isolate; padding: 0; overflow: hidden; background: #243746; }
.hero-image { position: absolute; inset: 0; width: 100%; height: 100%; object-fit: cover; object-position: 50% 61%; transform: scale(1.12); transform-origin: 50% 70%; z-index: -2; }
.hero-shade { position: absolute; inset: 0; z-index: -1; background: linear-gradient(180deg, rgba(12,22,34,.38), rgba(12,22,34,.04) 29%, rgba(12,22,34,.08) 52%, rgba(12,22,34,.78)), linear-gradient(90deg, rgba(12,22,34,.5), rgba(12,22,34,.08) 70%); }
.hero-copy { display: flex; width: min(100%, 43rem); height: 100%; flex-direction: column; align-items: flex-start; justify-content: space-between; padding: clamp(3.25rem, 11svh, 5.25rem) 1.2rem 1.4rem; color: white; }
.hero-title { max-width: 22rem; }
.hero-action-area { max-width: min(19rem, 76vw); }
.eyebrow { margin: 0 0 .8rem; color: #e7f3f0; font-size: .79rem; letter-spacing: .12em; }
h1, h2, h3, p { margin-top: 0; }
h1 { max-width: 10em; margin-bottom: 0; font-size: clamp(2.35rem, 10.2vw, 5.35rem); line-height: 1.08; letter-spacing: -.06em; }
.lede { max-width: 31rem; margin-bottom: 1.15rem; font-size: clamp(.98rem, 3.7vw, 1.16rem); color: rgba(255,255,255,.94); }
.primary-link { display: inline-flex; min-height: 3rem; gap: .55rem; align-items: center; padding: .75rem 1.05rem; border-radius: 999px; color: var(--ink); background: var(--paper); box-shadow: 0 .7rem 1.6rem rgba(7,17,28,.18); font-weight: 700; text-decoration: none; touch-action: manipulation; }
.primary-link span { display: inline-block; animation: hero-scroll-hint 2.4s ease-in-out infinite; }
@keyframes hero-scroll-hint { 0%, 100% { transform: translateY(0); } 50% { transform: translateY(.18rem); } }

.scroll-journey { position: relative; display: grid; min-height: 33rem; overflow: hidden; background: #243746; }
.scroll-journey img { width: 100%; height: 100%; min-height: 33rem; object-fit: cover; object-position: 50% 36%; }
.scroll-journey p { position: absolute; left: 1rem; bottom: 1.25rem; max-width: 17rem; margin: 0; padding: .75rem .85rem; border: 1px solid rgba(255,255,255,.2); border-radius: .75rem; color: white; background: rgba(16,28,40,.54); backdrop-filter: blur(7px); }

.page-section { position: relative; padding: 4.7rem 1rem; border-bottom: 1px solid var(--line); scroll-margin-top: 4.2rem; }
.page-section:nth-child(even) { background: rgba(235,228,216,.48); }
.content-grid { width: min(100%, 74rem); margin: 0 auto; }
.section-kicker { display: inline-flex; align-items: center; gap: .45rem; margin-bottom: .8rem; color: var(--orange); font-size: .76rem; font-weight: 700; letter-spacing: .12em; }
.section-kicker::before { width: 1.75rem; height: 1px; content: ""; background: currentColor; }
h2 { max-width: 13em; margin-bottom: 1rem; font-size: clamp(2rem, 8.5vw, 4.2rem); letter-spacing: -.05em; line-height: 1.15; }
.section-intro { max-width: 45rem; color: #3c4c58; font-size: 1.05rem; }
.chapter-image { width: 100%; margin: 1.85rem 0; border-radius: var(--radius); aspect-ratio: 4 / 3; object-fit: cover; background: var(--paper-deep); box-shadow: 0 1rem 2.4rem rgba(24,37,53,.08); }
.chapter-image.portrait { aspect-ratio: 7 / 9; object-position: center; }
.chapter-image.square { aspect-ratio: 1; }
.chapter-image.wide { aspect-ratio: 16 / 9; }
.chapter-image.cover { aspect-ratio: 3 / 4; }
.image-caption { margin: -1.05rem 0 1.8rem; color: var(--muted); font-size: .78rem; }

.note-grid, .path-grid, .tool-grid, .semester-grid { display: grid; gap: .75rem; margin-top: 1.7rem; }
.note, .path-card, .tool-card, .semester { padding: 1rem; border: 1px solid var(--line); border-radius: 1rem; background: var(--card); }
.note strong, .path-card strong, .tool-card strong, .semester strong { display: block; margin-bottom: .25rem; font-size: 1rem; }
.note p, .path-card p, .tool-card p, .semester p { margin: 0; color: var(--muted); font-size: .92rem; }
.path-card img, .tool-card img { width: 100%; margin: 0 0 .85rem; border-radius: .75rem; object-fit: cover; }
.path-card img { aspect-ratio: 8 / 5; }
.tool-card img { aspect-ratio: 16 / 9; }
.action-list { display: grid; gap: .8rem; padding: 0; list-style: none; }
.action-list li { display: grid; grid-template-columns: 2.1rem 1fr; gap: .7rem; align-items: start; padding: .8rem 0; border-top: 1px solid var(--line); }
.action-list b { display: grid; place-items: center; width: 2.1rem; height: 2.1rem; border-radius: 50%; color: white; background: var(--ink); font-size: .8rem; }
.action-list--periods .action-period { align-content: center; justify-items: center; padding: .12rem; font-size: .7rem; font-weight: 700; line-height: 1.05; letter-spacing: -.04em; text-align: center; }
.action-list--periods .action-period--term { grid-template-rows: .72rem .68rem; gap: 0; padding-block: .3rem; letter-spacing: 0; }
.action-period--term span:first-child { font-size: .76rem; line-height: .72rem; }
.action-period--term span:last-child { font-size: .57rem; line-height: .68rem; white-space: nowrap; }
.quote { margin: 2rem 0 0; padding: 1.15rem 1.2rem; border-left: .22rem solid var(--orange); border-radius: 0 .9rem .9rem 0; background: rgba(255,255,255,.55); font-size: 1.05rem; }

/* Chapter 02 — timeline story. Data attributes reserve unified reveal and SVG draw behavior for a later phase. */
#coordinates .section-body { margin-top: 2.5rem; }
.timeline-story { position: relative; display: grid; gap: 1.3rem; padding-left: 2.05rem; }
.timeline-rail { position: absolute; inset: 0 auto 0 0; width: 1.05rem; height: 100%; overflow: visible; }
.timeline-rail path { fill: none; stroke: rgba(24,37,53,.24); stroke-width: 1.5; vector-effect: non-scaling-stroke; }
.story-card { position: relative; display: grid; gap: 1rem; padding: 1.25rem; border: 1px solid var(--line); border-radius: 1.15rem; background: rgba(255,255,255,.42); }
.timeline-marker { position: absolute; top: 1.55rem; right: calc(100% + 1.1rem); width: 1.02rem; height: 1.02rem; overflow: visible; }
.timeline-marker circle { fill: var(--paper); stroke: var(--orange); stroke-width: 3; }
.story-card__year { margin-bottom: .45rem; color: var(--orange); font-size: .76rem; font-weight: 700; letter-spacing: .11em; }
.story-card h3 { margin-bottom: .55rem; font-size: clamp(1.45rem, 6.2vw, 2rem); letter-spacing: -.04em; line-height: 1.16; }
.story-card__flow { margin-bottom: .75rem; color: #3c4c58; font-size: .88rem; font-weight: 700; letter-spacing: .02em; }
.story-card__lead { margin-bottom: .55rem; color: var(--ink); font-size: 1.02rem; font-weight: 650; line-height: 1.45; }
.story-card__body { margin: 0; color: var(--muted); }
.story-media { position: relative; display: grid; min-height: 0; margin: 0; overflow: hidden; border: 1px solid rgba(24,37,53,.16); border-radius: .9rem; background: linear-gradient(135deg, rgba(145,207,194,.26), rgba(156,138,202,.2)); }
.story-media--a, .story-media--b { aspect-ratio: 4 / 3; }
.story-media--c { aspect-ratio: 2 / 1; }
.story-media--image { aspect-ratio: 2 / 3; background: var(--paper-deep); }
.story-media--image::before { display: none; }
.story-media--image img { width: 100%; height: 100%; object-fit: cover; }
.story-media--observe img { object-position: 50% 58%; }
.story-media--create img { object-position: 50% 54%; }
.story-media--express img { object-position: 50% 50%; }
.story-media::before { position: absolute; inset: 0; content: ""; background: linear-gradient(90deg, transparent 49.85%, rgba(24,37,53,.12) 50%, transparent 50.15%), linear-gradient(transparent 49.85%, rgba(24,37,53,.12) 50%, transparent 50.15%); opacity: .6; }
.story-media__safe { position: absolute; inset: 10%; display: grid; align-content: center; justify-items: center; gap: .1rem; border: 1px dashed rgba(24,37,53,.35); border-radius: .45rem; color: var(--muted); text-align: center; letter-spacing: .04em; }
.story-media__safe span { font-size: .74rem; font-weight: 700; }
.story-media__safe small { font-size: .65rem; letter-spacing: .08em; }
/* Chapter 03 — an information-dense but quiet local tool ecosystem, not a directory. */
.ai-ecosystem { margin-top: clamp(2.7rem, 8vw, 5rem); padding: clamp(1.25rem, 5vw, 2.6rem); border: 1px solid var(--line); border-radius: var(--radius); background: rgba(255,255,255,.42); }
.ai-ecosystem__heading { max-width: 36rem; }
.ai-ecosystem__eyebrow { margin-bottom: .55rem; color: var(--orange); font-size: .76rem; font-weight: 700; letter-spacing: .11em; }
.ai-ecosystem__heading h3 { margin-bottom: .55rem; font-size: clamp(1.65rem, 7vw, 2.6rem); letter-spacing: -.045em; line-height: 1.12; }
.ai-ecosystem__heading > p:last-child { margin-bottom: 0; color: var(--muted); }
.ai-ecosystem__axis { display: flex; align-items: center; gap: .65rem; margin: 1.25rem 0 1.45rem; color: var(--muted); }
.ai-ecosystem__axis > span { display: grid; flex: 0 0 auto; width: 2.6rem; aspect-ratio: 1; place-items: center; border: 1px solid rgba(233,131,79,.48); border-radius: 50%; color: var(--ink); background: rgba(247,243,235,.9); font-size: 1rem; font-weight: 750; letter-spacing: -.07em; }
.ai-ecosystem__axis i { width: clamp(1rem, 7vw, 2.5rem); height: 1px; background: rgba(24,37,53,.22); }
.ai-ecosystem__axis small { font-size: .75rem; letter-spacing: .02em; }
.ai-tool-groups { display: grid; gap: 1.45rem; }
.ai-tool-group { min-width: 0; }
.ai-tool-group h4 { display: flex; align-items: center; gap: .55rem; margin: 0 0 .65rem; color: #3c4c58; font-size: .82rem; font-weight: 700; letter-spacing: .08em; }
.ai-tool-group h4::after { flex: 1; height: 1px; content: ""; background: var(--line); }
.ai-tool-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: .6rem; }
.ai-tool-card { display: grid; grid-template-rows: 2.45rem auto minmax(2.2rem, 1fr); gap: .35rem; min-width: 0; min-height: 8.4rem; padding: .75rem; border: 1px solid rgba(24,37,53,.12); border-radius: .9rem; background: rgba(247,243,235,.65); box-shadow: 0 .4rem .9rem rgba(24,37,53,.035); }
.ai-tool-card__logo { display: grid; width: 2.35rem; height: 2.35rem; place-items: center; overflow: hidden; border: 1px solid rgba(24,37,53,.1); border-radius: .68rem; background: rgba(255,255,255,.76); }
.ai-tool-card__logo img { display: block; width: 1.72rem; height: 1.72rem; object-fit: contain; }
.ai-tool-card strong { overflow-wrap: anywhere; color: var(--ink); font-size: clamp(.82rem, 3.7vw, .98rem); font-weight: 700; line-height: 1.18; letter-spacing: -.025em; }
.ai-tool-card p { margin: 0; overflow-wrap: anywhere; color: var(--muted); font-size: clamp(.68rem, 3vw, .76rem); line-height: 1.43; }
.ai-ecosystem__closing { max-width: 23rem; margin: 1.65rem auto 0; color: #3c4c58; text-align: center; font-size: clamp(.95rem, 3.6vw, 1.08rem); line-height: 1.7; }
.site-footer { display: grid; gap: 1rem; padding: 3rem 1rem calc(3rem + env(safe-area-inset-bottom)); color: #e7eced; background: var(--ink); }
.site-footer p { max-width: 30rem; margin: 0; font-size: 1.15rem; }
.site-footer a { color: #c3ece4; }

@media (min-width: 700px) {
  .site-header { padding-inline: clamp(1.5rem, 5vw, 4rem); }
  .hero { height: min(47rem, calc(92svh - 4.1rem)); min-height: min(47rem, calc(92svh - 4.1rem)); }
  .hero-copy { padding: 5.75rem clamp(1.8rem, 8vw, 7rem) 3.5rem; }
  .hero-action-area { max-width: 29rem; }
  .scroll-journey { min-height: 42rem; }
  .scroll-journey img { min-height: 42rem; }
  .scroll-journey p { left: clamp(1.5rem, 8vw, 7rem); bottom: 2rem; }
  .page-section { padding-block: 6rem; }
  .note-grid { grid-template-columns: repeat(3, 1fr); }
  .path-grid { grid-template-columns: repeat(2, 1fr); }
  .tool-grid { grid-template-columns: repeat(2, 1fr); }
  .semester-grid { grid-template-columns: repeat(2, 1fr); }
  .chapter-image { max-height: 40rem; }
  .story-media--image { aspect-ratio: 3 / 4; }
  .site-footer { padding-inline: clamp(1.5rem, 8vw, 7rem); }
}

@media (min-width: 1050px) {
  .page-section { padding-inline: clamp(2rem, 8vw, 10rem); }
  .content-grid { display: grid; grid-template-columns: minmax(16rem, .8fr) minmax(0, 1.5fr); column-gap: 6rem; }
  .section-heading { grid-column: 1; position: sticky; top: 7rem; align-self: start; }
  .section-body { grid-column: 2; }
  .chapter-image { margin-top: 0; }
  .path-grid { grid-template-columns: repeat(2, 1fr); }
  .tool-grid { grid-template-columns: repeat(2, 1fr); }
  #coordinates .content-grid { display: block; }
  #coordinates .section-heading { position: static; max-width: 43rem; }
  #coordinates .section-body { margin-top: 4rem; }
  .timeline-story { grid-template-columns: minmax(0, 1fr) 4.75rem minmax(0, 1fr); gap: 2.6rem 0; padding: 0; }
  .timeline-rail { position: relative; grid-column: 2; grid-row: 1 / span 3; width: 100%; height: 100%; }
  .story-card { width: min(100%, 31rem); padding: 1.65rem; }
  .story-card--one, .story-card--three { grid-column: 1; justify-self: end; }
  .story-card--two { grid-column: 3; justify-self: start; }
  .timeline-marker { top: 1.82rem; right: auto; left: calc(100% + 2.05rem); }
  .story-card--two .timeline-marker { right: calc(100% + 2.05rem); left: auto; }
  .ai-tool-groups { gap: 1.8rem; }
  .ai-tool-grid { grid-template-columns: repeat(auto-fit, minmax(8.25rem, 1fr)); gap: .75rem; }
  .ai-tool-card { min-height: 8.7rem; padding: .85rem; }
}

@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } .primary-link span { animation: none; } }