/* 善徙 · 黄河改道两千年 —— 纸上舆图风格 */
:root {
  --paper: #F2EBDB;
  --paper-deep: #EAE0C9;
  --ink: #2B251C;
  --ink-soft: #5C5342;
  --faint: #B0A385;
  --line: #D6C9AB;
  --sea: #DCE4DE;
  --vermilion: #A63A2B;
  --bronze: #8A5A44;
  --serif: "Noto Serif SC", "Source Han Serif SC", "Songti SC", "STSong", "SimSun", serif;
  --sans: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  background: var(--paper);
  color: var(--ink);
  font-family: var(--serif);
  -webkit-font-smoothing: antialiased;
  line-height: 1.9;
}
::selection { background: var(--vermilion); color: var(--paper); }

/* ---------- 顶栏 ---------- */
.topbar {
  position: fixed; inset: 0 0 auto 0; z-index: 50;
  display: flex; justify-content: space-between; align-items: center;
  padding: 14px 28px;
  background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: blur(6px);
  border-bottom: 1px solid var(--line);
}
.brand { font-size: 15px; letter-spacing: .12em; font-weight: 700; }
.brand em { font-style: normal; color: var(--vermilion); margin-right: 8px; }
.topbar nav { display: flex; gap: 22px; }
.topbar nav a {
  color: var(--ink-soft); text-decoration: none;
  font-family: var(--sans); font-size: 13px; letter-spacing: .1em;
}
.topbar nav a:hover { color: var(--vermilion); }

/* ---------- 英豪区 ---------- */
.hero {
  min-height: 100vh; position: relative;
  max-width: 1200px; margin: 0 auto; padding: 150px 28px 60px;
  display: flex; flex-direction: column; justify-content: center;
}
.hero-kicker {
  font-family: var(--sans); font-size: 14px; letter-spacing: .5em;
  color: var(--ink-soft); margin-bottom: 18px;
}
.hero-kicker b { color: var(--vermilion); font-weight: 400; padding: 0 2px; }
.hero-row { display: flex; align-items: baseline; gap: 28px; flex-wrap: wrap; }
.hero h1 {
  font-size: clamp(96px, 17vw, 210px);
  font-weight: 900; letter-spacing: .06em; line-height: 1.05;
}
.seal {
  display: inline-flex; align-items: center; justify-content: center;
  width: 52px; height: 52px; flex: none; align-self: center;
  background: var(--vermilion); color: var(--paper);
  font-size: 21px; font-weight: 700; line-height: 1.1;
  writing-mode: vertical-rl; letter-spacing: .18em;
  border-radius: 3px; transform: rotate(-2.5deg);
  box-shadow: inset 0 0 0 2px color-mix(in srgb, var(--paper) 55%, transparent);
}
.hero-sub { margin-top: 26px; font-size: 19px; letter-spacing: .06em; }
.hero-sub em { font-style: normal; color: var(--vermilion); }
.hero-lede {
  margin-top: 14px; max-width: 560px;
  color: var(--ink-soft); font-size: 15.5px;
}
.proverb {
  position: absolute; right: 34px; top: 50%; transform: translateY(-56%);
  writing-mode: vertical-rl; letter-spacing: .55em;
  font-size: 16px; color: var(--ink-soft);
  border-right: 1px solid var(--line); padding-right: 16px; height: 300px;
}
.hero-stats {
  margin-top: 64px; display: grid; grid-template-columns: repeat(4, 1fr);
  border-top: 1px solid var(--ink); 
}
.stat { padding: 18px 8px 0 0; }
.stat + .stat { padding-left: 22px; border-left: 1px solid var(--line); }
.stat-num { font-size: 34px; font-weight: 700; line-height: 1.2; }
.stat-label { font-family: var(--sans); font-size: 12.5px; color: var(--ink-soft); letter-spacing: .06em; }
.hero-hint {
  margin-top: 56px; font-family: var(--sans); font-size: 12.5px;
  color: var(--faint); letter-spacing: .3em;
}

/* ---------- 通用地图框 ---------- */
.map-frame {
  position: relative; background: var(--sea);
  border: 1px solid var(--line); border-radius: 4px; overflow: hidden;
}
.map-frame svg { display: block; }
.map-note {
  position: absolute; right: 10px; bottom: 8px; z-index: 4;
  font-family: var(--sans); font-size: 10.5px; color: #7d8a83;
  letter-spacing: .05em; pointer-events: none;
}

/* 地图元素 */
.prov { fill: #F5EFDF; stroke: #C7B892; stroke-width: .6; }
.prov-label { fill: #B3A78A; font-family: var(--sans); font-size: 13px; letter-spacing: .5em; text-anchor: middle; }
.sea-label { fill: #93A69C; font-family: var(--sans); font-size: 14px; letter-spacing: .6em; text-anchor: middle; }
.ref { fill: none; stroke-linecap: round; }
.lake { fill: #CBDAD3; stroke: #9FB4A6; stroke-width: .7; }
.dike { fill: none; stroke-width: 2; stroke-dasharray: 9 4; }
.course {
  fill: none; stroke-linecap: round; stroke-linejoin: round;
  cursor: pointer; vector-effect: non-scaling-stroke;
}
.course.hover { stroke-width: 4.5px !important; stroke-opacity: 1; }
.course-label {
  font-family: var(--sans); font-size: 11.5px; letter-spacing: .18em; text-anchor: middle;
  paint-order: stroke; stroke: var(--paper); stroke-width: 3.5px; cursor: pointer;
}
.breach .core { fill: var(--vermilion); stroke: var(--paper); stroke-width: 1; }
.breach .pulse { fill: none; stroke: var(--vermilion); opacity: 0; }
.breach-label {
  font-family: var(--sans); font-size: 11px; fill: #4A4234;
  paint-order: stroke; stroke: #EDE9DC; stroke-width: 3px;
}
.city circle { fill: var(--ink); opacity: .72; }
.city text { font-family: var(--sans); font-size: 11px; fill: #4A4234; paint-order: stroke; stroke: #EDE9DC; stroke-width: 3px; }
.city.tier1 circle { r: 3; } .city.tier1 text { font-size: 12px; font-weight: 600; }
.callout-line { stroke: var(--vermilion); stroke-width: 1; stroke-dasharray: 2 2; }
.callout-dot { fill: var(--vermilion); }
.callout-text .t1 { font-family: var(--sans); font-weight: 700; font-size: 13px; fill: var(--vermilion); }
.callout-text .t2 { font-family: var(--sans); font-size: 11px; fill: var(--ink-soft); paint-order: stroke; stroke: #EDE9DC; stroke-width: 3px; }
.map-tip {
  position: absolute; z-index: 8; pointer-events: none; opacity: 0;
  background: rgba(43, 37, 28, .94); color: #F2EBDB;
  padding: 8px 11px; border-radius: 3px; max-width: 230px;
  font-family: var(--sans); font-size: 12px; line-height: 1.5;
  transition: opacity .15s;
}
.map-tip b { display: block; margin-bottom: 2px; letter-spacing: .04em; }
.map-tip span { display: block; font-size: 11px; opacity: .82; }

/* ---------- 滚动叙事 ---------- */
.section-head { max-width: 1200px; margin: 0 auto; padding: 90px 28px 34px; }
.section-head .zh { font-size: 34px; font-weight: 800; letter-spacing: .1em; }
.section-head .zh::after { content: ""; display: block; width: 46px; border-top: 3px solid var(--vermilion); margin-top: 14px; }
.section-head p { margin-top: 14px; color: var(--ink-soft); font-size: 15px; max-width: 640px; }
.scrolly {
  max-width: 1200px; margin: 0 auto; padding: 0 28px 60px;
  display: grid; grid-template-columns: minmax(320px, 460px) 1fr; gap: 52px;
  align-items: start;
}
.steps { display: block; }
.step { padding: 16vh 0; opacity: .3; transition: opacity .45s; }
.step.active { opacity: 1; }
.step-kicker {
  display: flex; gap: 14px; align-items: baseline;
  font-family: var(--sans); font-size: 12.5px; letter-spacing: .18em; color: var(--vermilion);
}
.step-kicker span + span { color: var(--ink-soft); }
.step-title { font-size: 30px; font-weight: 800; letter-spacing: .05em; margin: 10px 0 18px; }
.step p { font-size: 16px; line-height: 2.05; color: #3A342A; }
.step p + p { margin-top: 12px; }
.scrolly-map-col {
  position: sticky; top: 74px;
  height: calc(100vh - 100px); min-height: 480px;
}
.scrolly-map { height: 100%; }

/* ---------- 交互探索 ---------- */
.explorer { max-width: 1280px; margin: 0 auto; padding: 0 28px 80px; }
.explorer-controls { margin-top: 8px; }
.era-btns { display: flex; flex-wrap: wrap; gap: 8px; }
.era-btn {
  font-family: var(--serif); background: none; cursor: pointer;
  border: 1px solid var(--line); border-radius: 3px;
  padding: 7px 13px 6px; text-align: left; color: var(--ink);
  transition: all .18s;
}
.era-btn .era-year { display: block; font-size: 15px; font-weight: 700; line-height: 1.3; }
.era-btn .era-short { display: block; font-family: var(--sans); font-size: 10.5px; color: var(--ink-soft); letter-spacing: .12em; }
.era-btn:hover { border-color: var(--ink-soft); }
.era-btn.active { background: var(--ink); border-color: var(--ink); color: var(--paper); }
.era-btn.active .era-short { color: rgba(242, 235, 219, .75); }

.slider-block { margin: 30px 0 8px; position: relative; }
#year-slider { width: 100%; accent-color: var(--vermilion); height: 26px; cursor: ew-resize; }
.slider-ticks { position: relative; height: 30px; font-family: var(--sans); font-size: 10px; color: var(--faint); }
.tick { position: absolute; transform: translateX(-50%); text-align: center; white-space: nowrap; }
.tick i { display: block; width: 1px; height: 5px; background: var(--faint); margin: 0 auto 2px; }

.explorer-actions { display: flex; gap: 10px; margin: 18px 0 14px; flex-wrap: wrap; }
.btn {
  font-family: var(--sans); font-size: 13px; letter-spacing: .14em;
  padding: 9px 20px; border-radius: 3px; cursor: pointer; transition: all .18s;
  background: var(--vermilion); color: var(--paper); border: 1px solid var(--vermilion);
}
.btn:hover { filter: brightness(1.08); }
.btn.ghost { background: none; color: var(--ink); border-color: var(--line); }
.btn.ghost:hover, .btn.ghost.on { border-color: var(--ink); background: var(--ink); color: var(--paper); }
.toggles { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 22px; }
.chip { font-family: var(--sans); font-size: 12px; color: var(--ink-soft); cursor: pointer; }
.chip input { display: none; }
.chip span {
  display: inline-block; padding: 4px 11px; border: 1px solid var(--line);
  border-radius: 999px; transition: all .15s; user-select: none;
}
.chip input:checked + span { background: var(--paper-deep); border-color: var(--bronze); color: var(--ink); }

.explorer-grid { display: grid; grid-template-columns: 1fr 320px; gap: 26px; align-items: stretch; }
#explorer-map { height: 74vh; min-height: 520px; }
.side-col { display: flex; flex-direction: column; gap: 18px; min-height: 0; }

.event-card {
  background: var(--paper-deep); border: 1px solid var(--line); border-radius: 4px;
  padding: 20px 20px 16px; overflow-y: auto;
}
.card-era { font-family: var(--sans); font-size: 12.5px; letter-spacing: .25em; color: var(--vermilion); }
.card-title { font-size: 22px; font-weight: 800; margin: 6px 0 14px; letter-spacing: .04em; }
.card-meta { display: grid; gap: 6px; border-top: 1px solid var(--line); padding-top: 12px; }
.card-meta > div { display: flex; gap: 10px; font-family: var(--sans); }
.card-meta dt { flex: none; width: 34px; font-size: 11px; color: var(--faint); letter-spacing: .2em; padding-top: 2px; }
.card-meta dd { font-size: 12.5px; color: var(--ink); line-height: 1.6; }
.tag-nature { }
.tag-nature.is-renwei, dd.nature-人为 { color: var(--vermilion); }
.card-brief { margin-top: 12px; font-size: 13.5px; line-height: 1.95; color: #453E31; }

#legend { overflow-y: auto; flex: 1; min-height: 0; padding-right: 4px; }
.legend-item { display: flex; gap: 10px; padding: 7px 6px; border-radius: 3px; cursor: default; }
.legend-item:hover { background: var(--paper-deep); }
.swatch { flex: none; width: 22px; height: 0; border-top: 3px solid; margin-top: 10px; }
.legend-name { font-size: 13.5px; font-weight: 700; line-height: 1.5; }
.legend-name em { font-style: normal; font-family: var(--sans); font-weight: 400; font-size: 10.5px; color: var(--faint); margin-left: 6px; }
.legend-sub { font-family: var(--sans); font-size: 11px; color: var(--ink-soft); line-height: 1.5; }

/* ---------- 附录 ---------- */
.appendix { max-width: 1200px; margin: 0 auto; padding: 0 28px 90px; }
.table-wrap { overflow-x: auto; border-top: 2px solid var(--ink); }
table { width: 100%; border-collapse: collapse; min-width: 760px; }
th {
  font-family: var(--sans); font-weight: 400; font-size: 12px; letter-spacing: .2em;
  color: var(--ink-soft); text-align: left; padding: 14px 12px 10px;
  border-bottom: 1px solid var(--line);
}
td { padding: 13px 12px; border-bottom: 1px solid var(--line); font-size: 14.5px; vertical-align: top; }
.td-year { font-weight: 700; white-space: nowrap; }
.td-year em { display: block; font-style: normal; font-family: var(--sans); font-size: 11px; color: var(--ink-soft); font-weight: 400; }
.tag { font-family: var(--sans); font-size: 11px; padding: 2px 9px; border-radius: 999px; letter-spacing: .15em; white-space: nowrap; }
.tag-自然 { background: var(--paper-deep); color: var(--bronze); border: 1px solid var(--bronze); }
.tag-人为 { background: var(--vermilion); color: var(--paper); border: 1px solid var(--vermilion); }
.tag-治理 { background: none; color: var(--ink-soft); border: 1px solid var(--line); }
.footnote { margin-top: 14px; font-family: var(--sans); font-size: 12px; color: var(--ink-soft); }
.sources { margin-top: 10px; padding-left: 20px; font-family: var(--sans); font-size: 12.5px; color: var(--ink-soft); line-height: 2.1; }

footer {
  border-top: 1px solid var(--line); padding: 34px 28px 44px; text-align: center;
  font-family: var(--sans); font-size: 12px; color: var(--faint); letter-spacing: .12em;
}

/* ---------- 响应式 ---------- */
@media (max-width: 920px) {
  .topbar { padding: 10px 16px; }
  .topbar nav { gap: 14px; }
  .topbar nav a:not(.keep) { display: none; }
  .hero { padding: 110px 20px 40px; }
  .proverb { display: none; }
  .hero-stats { grid-template-columns: repeat(2, 1fr); row-gap: 18px; }
  .stat + .stat { padding-left: 16px; }
  .scrolly { display: flex; flex-direction: column; gap: 0; padding: 0 16px 40px; }
  .scrolly-map-col { order: -1; top: 58px; height: 46vh; min-height: 340px; margin-bottom: 8px; z-index: 5; }
  .scrolly-map { min-height: 0; }
  .step { padding: 8vh 0; }
  .step-title { font-size: 24px; }
  .explorer-grid { grid-template-columns: 1fr; }
  #explorer-map { height: 58vh; min-height: 380px; }
  .era-btns { overflow-x: auto; flex-wrap: nowrap; padding-bottom: 6px; }
  .era-btn { flex: none; }
}