/* ==================================================================
   Out of Africa — evidence timeline
   Desktop: timelines run horizontally, driven by scroll.
   Mobile (<900px): the same rails become vertical stacks.
   ================================================================== */

:root {
  --bg:        #080c11;
  --bg-2:      #0b1219;
  --bg-3:      #101a23;
  --ink:       #eef2f5;
  --ink-2:     #a8b6c2;
  --ink-3:     #6d7e8c;
  --line:      #1d2a35;
  --sand:      #c9a77a;
  --sand-dim:  #8a6c47;
  --teal:      #4fd1c5;
  --amber:     #e8a33d;
  --rust:      #d9634a;
  --ocean:     #12303f;

  --est:  #4fd1c5;
  --deb:  #e8a33d;
  --con:  #d9634a;

  --display: "Fraunces", Georgia, serif;
  --sans:    "Inter", system-ui, -apple-system, sans-serif;
  --mono:    "JetBrains Mono", ui-monospace, "SF Mono", monospace;

  --pad: clamp(1.25rem, 5vw, 5rem);
  --maxw: 74rem;
}

*, *::before, *::after { box-sizing: border-box; }

html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  font-weight: 300;
  line-height: 1.6;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3 { font-family: var(--display); font-weight: 600; line-height: 1.05; margin: 0; letter-spacing: -0.02em; }
p { margin: 0 0 1.1em; }
a { color: var(--teal); text-decoration: none; border-bottom: 1px solid rgba(79,209,197,.28); }
a:hover { border-bottom-color: var(--teal); }
em { font-style: italic; }

.wrap { max-width: var(--maxw); margin: 0 auto; padding-inline: var(--pad); }

.kicker {
  font-family: var(--mono);
  font-size: .72rem;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--sand);
  margin-bottom: 1.1rem;
}

.prose { color: var(--ink-2); max-width: 46rem; font-size: clamp(1rem, 1.5vw, 1.12rem); }
.fineprint { color: var(--ink-3); font-size: .82rem; line-height: 1.65; }

/* ---------------------------- progress rail ---------------------- */
.progress-rail {
  position: fixed; inset: 0 0 auto 0; height: 2px; z-index: 90;
  background: rgba(255,255,255,.05);
}
.progress-fill {
  height: 100%; width: 0;
  background: linear-gradient(90deg, var(--sand), var(--teal));
  transition: width .08s linear;
}

/* -------------------------------- hero --------------------------- */
.hero {
  position: relative;
  min-height: 100svh;
  display: grid;
  align-items: center;
  overflow: hidden;
  border-bottom: 1px solid var(--line);
}

.hero-strata { position: absolute; inset: 0; z-index: 0; }
.hero-strata span {
  position: absolute; left: -10%; width: 120%;
  height: calc(100% / 8);
  top: calc(var(--i) * (100% / 8));
  background: linear-gradient(90deg,
    rgba(201,167,122,0) 0%,
    rgba(201,167,122, calc(0.015 + var(--i) * 0.011)) 45%,
    rgba(201,167,122,0) 100%);
  transform: translateX(calc(var(--i) * -2%));
  animation: drift calc(38s + var(--i) * 7s) ease-in-out infinite alternate;
}
@keyframes drift {
  from { transform: translateX(-6%) skewY(-.35deg); }
  to   { transform: translateX(6%)  skewY(.35deg); }
}

.hero-inner { position: relative; z-index: 1; max-width: var(--maxw); margin: 0 auto; padding: 6rem var(--pad) 5rem; width: 100%; }

h1 {
  font-size: clamp(3rem, 11vw, 8.5rem);
  font-weight: 800;
  letter-spacing: -0.045em;
  margin-bottom: 1.6rem;
}
h1 em { color: var(--sand); font-weight: 400; }

.lede { color: var(--ink-2); max-width: 40rem; font-size: clamp(1rem, 1.6vw, 1.18rem); }

.hero-meta { display: flex; gap: clamp(1.5rem, 5vw, 3.5rem); margin-top: 2.75rem; flex-wrap: wrap; }
.hero-meta div { display: flex; flex-direction: column; }
.hero-meta strong { font-family: var(--display); font-size: 2rem; font-weight: 600; color: var(--sand); line-height: 1; }
.hero-meta span { font-family: var(--mono); font-size: .68rem; letter-spacing: .14em; text-transform: uppercase; color: var(--ink-3); margin-top: .5rem; }

.scroll-cue {
  position: absolute; bottom: 2rem; left: var(--pad);
  font-family: var(--mono); font-size: .68rem; letter-spacing: .2em; text-transform: uppercase;
  color: var(--ink-3); display: flex; align-items: center; gap: .7rem;
}
.scroll-cue span { display: block; width: 2.5rem; height: 1px; background: var(--ink-3); transform-origin: left; animation: pulse 2.4s ease-in-out infinite; }
@keyframes pulse { 0%,100% { transform: scaleX(.3); opacity: .4; } 50% { transform: scaleX(1); opacity: 1; } }

/* ------------------------------ sections ------------------------- */
.section { padding: clamp(4rem, 11vw, 9rem) 0; border-bottom: 1px solid var(--line); }
.section h2, .act-intro h2 { font-size: clamp(1.9rem, 4.6vw, 3.4rem); margin-bottom: 1.4rem; }

.act-intro { padding: clamp(4rem, 12vw, 9rem) 0 clamp(2rem, 5vw, 3.5rem); }

/* --------------------------- scale chart ------------------------- */
.scale-chart { margin: 3rem 0 3.5rem; display: flex; flex-direction: column; gap: .55rem; }
.scale-row { display: grid; grid-template-columns: minmax(0,1fr); gap: .3rem; }
.scale-row .sr-top { display: flex; justify-content: space-between; align-items: baseline; gap: 1rem; }
.scale-row .sr-label { font-size: .87rem; color: var(--ink-2); }
.scale-row .sr-num { font-family: var(--mono); font-size: .74rem; color: var(--ink-3); white-space: nowrap; }
.scale-row .sr-bar { height: 9px; background: rgba(255,255,255,.04); border-radius: 2px; overflow: hidden; }
.scale-row .sr-bar i {
  display: block; height: 100%; width: 0; border-radius: 2px;
  transition: width 1.5s cubic-bezier(.16,1,.3,1);
}
.scale-row.rock .sr-bar i { background: linear-gradient(90deg, var(--sand-dim), var(--sand)); }
.scale-row.bone .sr-bar i { background: linear-gradient(90deg, #2c5d63, var(--teal)); min-width: 2px; }
.scale-row.is-in .sr-bar i { width: var(--w); }

.callout {
  border-left: 2px solid var(--sand);
  padding: 1.5rem 0 .4rem 1.75rem;
  max-width: 46rem;
}
.callout p { color: var(--ink-2); }
.callout p:last-child { margin-bottom: 0; }
.callout strong { color: var(--ink); font-weight: 500; }

/* ---------------------------- legend ----------------------------- */
.legend { list-style: none; padding: 0; margin: 2rem 0 0; display: flex; flex-wrap: wrap; gap: .6rem 2rem; }
.legend li { display: flex; align-items: center; gap: .6rem; font-size: .84rem; color: var(--ink-2); }
.dot { width: .6rem; height: .6rem; border-radius: 50%; flex: none; }
.dot.established { background: var(--est); }
.dot.debated     { background: var(--deb); }
.dot.contested   { background: var(--con); }

/* ======================= HORIZONTAL TRACKS ======================== */
.track-section { position: relative; }

.track-sticky {
  position: sticky; top: 0;
  height: 100svh;
  display: flex; flex-direction: column;
  overflow: hidden;
  border-block: 1px solid var(--line);
  background: var(--bg-2);
}

.track-head {
  flex: none;
  display: flex; align-items: center; gap: 1.25rem;
  padding: 1.1rem var(--pad);
  border-bottom: 1px solid var(--line);
  font-family: var(--mono); font-size: .68rem; letter-spacing: .16em; text-transform: uppercase;
  color: var(--ink-3);
}
.track-label { color: var(--sand); }
.track-hint { margin-left: auto; white-space: nowrap; }
.track-progress { flex: 1; height: 1px; background: rgba(255,255,255,.08); max-width: 22rem; }
.track-progress i { display: block; height: 100%; width: 0; background: var(--teal); }

.track-body { flex: 1; display: grid; grid-template-rows: minmax(0, 1.05fr) minmax(0, 1fr); min-height: 0; }
.track-body-single { grid-template-rows: minmax(0, 1fr); }

.rail-viewport { overflow: hidden; min-height: 0; display: flex; align-items: stretch; }
.rail {
  display: flex; align-items: stretch; gap: clamp(1rem, 2.5vw, 2rem);
  padding: clamp(.75rem, 2.5vh, 2rem) var(--pad);
  width: max-content; height: 100%;
  will-change: transform;
}

/* ---- stage cards (Act I) ---- */
.stage-card {
  flex: none; width: min(30rem, 78vw);
  border: 1px solid var(--line);
  border-top: 2px solid var(--sand-dim);
  background: linear-gradient(180deg, rgba(201,167,122,.05), rgba(255,255,255,.012));
  padding: 1.5rem 1.6rem 1.4rem;
  display: flex; flex-direction: column;
  opacity: .42; overflow-y: auto; scrollbar-width: thin;
  transition: opacity .45s ease, border-color .45s ease, transform .45s ease;
  transform: translateY(6px);
}
.stage-card.is-active { opacity: 1; border-top-color: var(--sand); transform: translateY(0); }
.stage-card .sc-when { font-family: var(--mono); font-size: .72rem; letter-spacing: .1em; color: var(--sand); margin-bottom: .7rem; }
.stage-card h3 { font-size: 1.4rem; margin-bottom: .8rem; }
.stage-card p { color: var(--ink-2); font-size: .92rem; }

.ev-list { list-style: none; margin: auto 0 0; padding: .9rem 0 0; border-top: 1px solid var(--line); display: flex; flex-direction: column; gap: .7rem; }
.ev-list li { font-size: .78rem; line-height: 1.5; }
.ev-list .ev-cite { color: var(--ink); border-bottom-color: rgba(238,242,245,.2); }
.ev-list .ev-note { color: var(--ink-3); display: block; margin-top: .2rem; }

/* ---- map stage ---- */
.mapstage { position: relative; min-height: 0; display: flex; flex-direction: column; padding: 0; }
#plateMap { width: 100%; height: 100%; min-height: 0; flex: 1; display: block; }
.mapstage-caption {
  flex: none; text-align: center; padding: .35rem 0 .6rem;
  font-family: var(--mono); font-size: .7rem; letter-spacing: .14em; text-transform: uppercase; color: var(--ink-3);
}

.land-layer path {
  fill: url(#landGrad); stroke: rgba(0,0,0,.4); stroke-width: 1.5;
  transition: transform 1.15s cubic-bezier(.65,0,.35,1), opacity .8s ease;
}
.shelf-layer path { fill: rgba(79,209,197,.16); stroke: rgba(79,209,197,.5); stroke-width: 1; stroke-dasharray: 5 4; transition: opacity .8s ease; opacity: 0; }
.ice-layer path { fill: rgba(226,240,247,.2); stroke: rgba(226,240,247,.45); stroke-width: 1; transition: opacity .8s ease; opacity: 0; }
.label-layer text {
  fill: rgba(238,242,245,.72); font-family: var(--mono); font-size: 13px; letter-spacing: .1em; text-anchor: middle;
  transition: transform 1.15s cubic-bezier(.65,0,.35,1), opacity .8s ease;
  paint-order: stroke; stroke: rgba(5,13,21,.85); stroke-width: 3px;
}
.mapstage.no-map .land-layer, .mapstage.no-map .label-layer { opacity: 0; }
.land-layer, .label-layer { transition: opacity .7s ease; }

/* ---- event cards (Act II) ---- */
.rail-human { align-items: center; }

.event-card {
  flex: none; width: min(24rem, 80vw);
  align-self: stretch;
  display: flex; flex-direction: column;
  border: 1px solid var(--line);
  background: linear-gradient(180deg, rgba(255,255,255,.035), rgba(255,255,255,.008));
  padding: 1.35rem 1.4rem 1.2rem;
  position: relative;
  opacity: .42; transform: translateY(10px);
  transition: opacity .5s ease, transform .5s ease, border-color .5s ease;
  overflow-y: auto; scrollbar-width: thin;
}
.event-card.is-active { opacity: 1; transform: translateY(0); }
.event-card::before {
  content: ""; position: absolute; inset: 0 0 auto 0; height: 2px; background: var(--line);
  transition: background .5s ease;
}
.event-card.c-established.is-active::before { background: var(--est); }
.event-card.c-debated.is-active::before     { background: var(--deb); }
.event-card.c-contested.is-active::before   { background: var(--con); }

.ec-top { display: flex; align-items: baseline; justify-content: space-between; gap: .8rem; margin-bottom: .55rem; }
.ec-age { font-family: var(--mono); font-size: .78rem; color: var(--sand); letter-spacing: .04em; }
.ec-conf { font-family: var(--mono); font-size: .62rem; letter-spacing: .14em; text-transform: uppercase; padding: .18rem .5rem; border: 1px solid currentColor; border-radius: 2px; white-space: nowrap; }
.c-established .ec-conf { color: var(--est); }
.c-debated .ec-conf     { color: var(--deb); }
.c-contested .ec-conf   { color: var(--con); }

.ec-place {
  display: flex; align-items: baseline; justify-content: space-between; gap: .8rem;
  font-family: var(--mono); font-size: .7rem; letter-spacing: .1em; text-transform: uppercase;
  color: var(--ink-3); margin-bottom: .85rem;
}
.ec-kind { color: rgba(255,255,255,.22); font-size: .6rem; letter-spacing: .16em; white-space: nowrap; }
.event-card h3 { font-size: 1.18rem; line-height: 1.2; margin-bottom: .7rem; }
.ec-body { color: var(--ink-2); font-size: .87rem; line-height: 1.62; margin-bottom: 1rem; }

.ec-method {
  font-size: .74rem; color: var(--ink-3); line-height: 1.5;
  border-left: 1px solid var(--line); padding-left: .8rem; margin-bottom: 1rem;
}
.ec-method b { color: var(--ink-2); font-weight: 500; display: block; font-family: var(--mono); font-size: .62rem; letter-spacing: .14em; text-transform: uppercase; margin-bottom: .25rem; }

.ec-sources { margin: auto 0 0; padding-top: .85rem; border-top: 1px solid var(--line); display: flex; flex-direction: column; gap: .45rem; }
.ec-sources a { font-size: .75rem; line-height: 1.45; color: var(--ink); border-bottom-color: rgba(238,242,245,.18); }
.ec-sources a:hover { color: var(--teal); border-bottom-color: var(--teal); }

/* era divider inserted into the human rail */
.era-mark {
  flex: none; align-self: center; width: 1px; background: var(--line); height: 60%;
  position: relative;
}
.era-mark span {
  position: absolute; top: -1.6rem; left: 50%; transform: translateX(-50%);
  font-family: var(--mono); font-size: .62rem; letter-spacing: .16em; text-transform: uppercase;
  color: var(--sand); white-space: nowrap;
}

/* ---------------------------- audit ------------------------------ */
.audit-grid { display: grid; gap: 1.25rem; margin-top: 3rem; grid-template-columns: repeat(auto-fit, minmax(min(100%, 26rem), 1fr)); }
.audit-card { border: 1px solid var(--line); padding: 1.6rem; background: rgba(255,255,255,.015); }
.audit-claim { font-family: var(--display); font-size: 1.08rem; line-height: 1.35; color: var(--ink); margin-bottom: .9rem; }
.audit-claim::before { content: "“"; color: var(--ink-3); }
.audit-claim::after  { content: "”"; color: var(--ink-3); }
.audit-verdict {
  display: inline-block; font-family: var(--mono); font-size: .64rem; letter-spacing: .14em; text-transform: uppercase;
  padding: .25rem .6rem; border: 1px solid currentColor; margin-bottom: 1rem;
}
.v-no    { color: var(--con); }
.v-mixed { color: var(--deb); }
.v-close { color: var(--deb); }
.v-yes   { color: var(--est); }
.audit-card p { color: var(--ink-2); font-size: .89rem; }
.audit-refs { list-style: none; padding: .9rem 0 0; margin: 0; border-top: 1px solid var(--line); }
.audit-refs li { font-family: var(--mono); font-size: .68rem; color: var(--ink-3); line-height: 1.7; }

/* --------------------------- sources ----------------------------- */
.source-list { margin: 2.5rem 0 0; padding-left: 1.4rem; columns: 2; column-gap: 3rem; }
.source-list li { break-inside: avoid; margin-bottom: .8rem; font-size: .82rem; line-height: 1.55; color: var(--ink-2); }
.source-list a { color: var(--ink); border-bottom-color: rgba(238,242,245,.16); }

.method-note { margin-top: 4rem; border-top: 1px solid var(--line); padding-top: 2.5rem; }
.method-note h3 { font-size: 1.4rem; margin-bottom: 1.5rem; }
.method-note dl { margin: 0 0 2rem; max-width: 46rem; }
.method-note dt { font-family: var(--mono); font-size: .72rem; letter-spacing: .1em; text-transform: uppercase; color: var(--sand); margin-top: 1.2rem; }
.method-note dd { margin: .4rem 0 0; color: var(--ink-2); font-size: .88rem; }

.foot { padding: 3.5rem 0 5rem; }
.foot p:first-child { font-family: var(--display); font-size: 1.05rem; color: var(--ink-2); }

/* ====================== MOBILE — GO VERTICAL ====================== */
@media (max-width: 900px) {
  .track-section { height: auto !important; }

  .track-sticky { position: static; height: auto; overflow: visible; }

  .track-head { position: sticky; top: 0; z-index: 20; background: var(--bg-2); }
  .track-hint { display: none; }

  .track-body { display: block; }

  /* the map pins to the top of the viewport while its stages scroll past */
  .mapstage {
    position: sticky; top: 3.1rem; z-index: 10;
    height: 44svh; background: var(--bg-2);
    border-bottom: 1px solid var(--line);
    padding-inline: 0;
  }

  .rail-viewport { overflow: visible; display: block; }

  /* the rail becomes a vertical spine */
  .rail {
    display: flex; flex-direction: column; gap: 0;
    width: auto; height: auto;
    padding: 2.5rem 0 3.5rem 0;
    transform: none !important;
    position: relative;
  }
  .rail::before {
    content: ""; position: absolute; left: 1.15rem; top: 0; bottom: 0; width: 1px;
    background: linear-gradient(180deg, transparent, var(--line) 6%, var(--line) 94%, transparent);
  }

  .stage-card, .event-card {
    width: auto; max-width: none; overflow: visible;
    margin: 0 var(--pad) 1.25rem calc(var(--pad) + 1.5rem);
    transform: translateY(14px);
  }
  .stage-card.is-active, .event-card.is-active { transform: translateY(0); }

  .stage-card::after, .event-card::after {
    content: ""; position: absolute; left: -1.9rem; top: 1.6rem;
    width: .55rem; height: .55rem; border-radius: 50%;
    background: var(--bg-2); border: 1px solid var(--ink-3);
    transition: background .4s ease, border-color .4s ease;
  }
  .stage-card { position: relative; }
  .stage-card.is-active::after { background: var(--sand); border-color: var(--sand); }
  .event-card.c-established.is-active::after { background: var(--est); border-color: var(--est); }
  .event-card.c-debated.is-active::after     { background: var(--deb); border-color: var(--deb); }
  .event-card.c-contested.is-active::after   { background: var(--con); border-color: var(--con); }

  .era-mark {
    width: auto; height: auto; background: none;
    margin: 1.5rem var(--pad) 1.5rem calc(var(--pad) + 1.5rem);
  }
  .era-mark span { position: static; transform: none; display: block; }

  .source-list { columns: 1; }
  .hero-meta { gap: 1.5rem 2.25rem; }
}

@media (max-width: 560px) {
  .mapstage { height: 38svh; }
  .stage-card, .event-card { padding: 1.15rem 1.1rem 1.05rem; }
}

/* ------------------------ reduced motion ------------------------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: .001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .001ms !important;
  }
  .stage-card, .event-card { opacity: 1 !important; transform: none !important; }
}