/* ============================================================
   Collection Studies — design system
   Palette carries over from the matplotlib "v2" charts:
   warm paper, ink, Sigg red, warm grey.
   ============================================================ */

:root{
  --paper:      #FBFAF7;
  --paper-2:    #F4F1EA;
  --ink:        #1C1B19;
  --ink-soft:   #3A3833;
  --sigg:       #E0452F;
  --sigg-dk:    #B5331F;
  --over:       #C3BCB0;
  --line:       #E3DED5;
  --muted:      #8C877E;

  --maxw: 1080px;
  --col:  740px;

  --serif: "Iowan Old Style","Palatino Linotype",Palatino,"Book Antiqua",Georgia,
           "Songti SC","STSong","SimSun","Noto Serif CJK SC","Source Han Serif SC","Noto Serif SC",serif;
  --sans:  -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Helvetica Neue",
           Arial,"PingFang SC","Hiragino Sans GB","Microsoft YaHei",
           "Noto Sans CJK SC","Source Han Sans SC","Noto Sans SC","WenQuanYi Micro Hei",sans-serif;

  --ease: cubic-bezier(.2,.6,.2,1);
}

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

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

body{
  margin:0;
  background:var(--paper);
  color:var(--ink);
  font-family:var(--sans);
  font-size:17px;
  line-height:1.68;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
}

img{ max-width:100%; height:auto; display:block; }

a{ color:inherit; text-decoration:none; }

::selection{ background:rgba(224,69,47,.16); }

/* ---------- layout ---------- */
.wrap{ width:100%; max-width:var(--maxw); margin:0 auto; padding:0 28px; }
.col{ width:100%; max-width:var(--col); margin:0 auto; }

/* ---------- header ---------- */
.site-header{
  position:sticky; top:0; z-index:50;
  background:rgba(251,250,247,.86);
  backdrop-filter:saturate(160%) blur(10px);
  -webkit-backdrop-filter:saturate(160%) blur(10px);
  border-bottom:1px solid var(--line);
}
.site-header .wrap{
  display:flex; align-items:center; justify-content:space-between;
  height:64px;
}
.brand{
  font-family:var(--serif);
  font-size:20px; letter-spacing:.01em;
  display:inline-flex; align-items:center; gap:9px;
}
.brand .dot{
  width:9px; height:9px; border-radius:50%;
  background:var(--sigg); display:inline-block;
}
.nav{ display:flex; gap:26px; align-items:center; }
.nav a{
  font-size:14px; letter-spacing:.02em; color:var(--ink-soft);
  position:relative; padding:2px 0; transition:color .2s var(--ease);
}
.nav a::after{
  content:""; position:absolute; left:0; right:100%; bottom:-2px;
  height:1.5px; background:var(--sigg); transition:right .28s var(--ease);
}
.nav a:hover{ color:var(--ink); }
.nav a:hover::after{ right:0; }
.nav a.is-active{ color:var(--ink); }
.nav a.is-active::after{ right:0; }

/* ---------- hero ---------- */
.hero{ padding:88px 0 64px; }
.kicker{
  font-size:12.5px; letter-spacing:.18em; text-transform:uppercase;
  color:var(--sigg); font-weight:600; margin:0 0 22px;
}
.hero h1{
  font-family:var(--serif); font-weight:600;
  font-size:clamp(2.3rem,5.6vw,4.1rem);
  line-height:1.04; letter-spacing:-.022em;
  margin:0 0 26px; max-width:15ch;
}
.lede{
  font-size:clamp(1.05rem,2.1vw,1.28rem);
  line-height:1.6; color:var(--ink-soft);
  max-width:44ch; margin:0 0 16px;
}
.hero .zh{
  font-family:var(--serif); color:var(--muted);
  font-size:15px; letter-spacing:.14em; margin:0 0 34px;
}
.actions{ display:flex; gap:14px; flex-wrap:wrap; align-items:center; }

/* ---------- buttons ---------- */
.btn{
  display:inline-flex; align-items:center; gap:9px;
  padding:11px 20px; border-radius:2px;
  font-size:14.5px; letter-spacing:.01em;
  border:1px solid var(--ink);
  background:var(--ink); color:var(--paper);
  transition:transform .2s var(--ease), background .2s var(--ease),
             color .2s var(--ease), border-color .2s var(--ease);
}
.btn:hover{ background:var(--sigg); border-color:var(--sigg); color:#fff;
            transform:translateY(-1px); }
.btn.ghost{ background:transparent; color:var(--ink); border-color:var(--line); }
.btn.ghost:hover{ border-color:var(--ink); background:transparent; color:var(--ink);
                  transform:translateY(-1px); }
.btn .arw{ transition:transform .2s var(--ease); }
.btn:hover .arw{ transform:translateX(3px); }

/* ---------- section ---------- */
.section{ padding:26px 0 10px; }
.section-head{
  display:flex; align-items:baseline; justify-content:space-between;
  gap:20px; border-top:1px solid var(--line);
  padding-top:22px; margin-bottom:30px;
}
.section-head h2{
  font-family:var(--serif); font-weight:600; font-size:26px;
  letter-spacing:-.01em; margin:0;
}
.section-head .more{ font-size:13.5px; color:var(--muted); }
.section-head .more:hover{ color:var(--sigg); }

/* ---------- KPI strip ---------- */
.kpis{
  display:grid; grid-template-columns:repeat(3,1fr);
  gap:24px; margin:8px 0 8px;
}
.kpi .num{
  font-family:var(--serif); font-weight:600;
  font-size:clamp(2.2rem,5vw,3.1rem); line-height:1;
  color:var(--sigg); letter-spacing:-.02em;
}
.kpi .label{
  font-size:13.5px; color:var(--muted); margin-top:10px;
  line-height:1.45; max-width:24ch;
}

/* ---------- cards ---------- */
.cards{ display:grid; grid-template-columns:1.4fr 1fr; gap:28px; align-items:start; }
.card{
  display:block; background:#fff; border:1px solid var(--line);
  border-radius:3px; overflow:hidden;
  transition:transform .26s var(--ease), box-shadow .26s var(--ease),
             border-color .26s var(--ease);
}
.card:hover{
  transform:translateY(-3px);
  box-shadow:0 16px 40px -22px rgba(28,27,25,.35);
  border-color:#d8d1c6;
}
.card .thumb{ background:var(--paper-2); overflow:hidden; }
.card .thumb img{ width:100%; transition:transform .5s var(--ease); }
.card:hover .thumb img{ transform:scale(1.025); }
.card .body{ padding:20px 22px 24px; }
.card .tag{
  font-size:11.5px; letter-spacing:.16em; text-transform:uppercase;
  color:var(--sigg); font-weight:600;
}
.card h3{
  font-family:var(--serif); font-weight:600; font-size:23px;
  line-height:1.2; letter-spacing:-.01em; margin:10px 0 8px;
}
.card p{ margin:0; color:var(--ink-soft); font-size:15px; line-height:1.6; }
.card .link{
  display:inline-flex; align-items:center; gap:7px; margin-top:16px;
  font-size:14px; color:var(--sigg); font-weight:500;
}
.card .link .arw{ transition:transform .2s var(--ease); }
.card:hover .link .arw{ transform:translateX(3px); }

/* muted "more" card */
.card.soon{
  background:var(--paper-2); border-style:dashed; color:var(--muted);
  display:flex; align-items:center; justify-content:center;
  min-height:100%; padding:38px 24px; text-align:center;
}
.card.soon:hover{ transform:none; box-shadow:none; border-color:var(--line); }
.card.soon .tag{ color:var(--over); }
.card.soon h3{ color:var(--ink-soft); font-size:19px; }
.card.soon p{ color:var(--muted); font-size:14px; }

/* ---------- notes list ---------- */
.notes{ list-style:none; margin:0; padding:0; }
.notes li{
  display:flex; gap:20px; padding:16px 0;
  border-bottom:1px solid var(--line); align-items:baseline;
}
.notes time{
  font-size:12.5px; color:var(--muted); letter-spacing:.04em;
  min-width:92px; flex:none; font-variant-numeric:tabular-nums;
}
.notes span{ font-size:15.5px; color:var(--ink-soft); }
.notes a:hover{ color:var(--sigg); }

/* ---------- article ---------- */
.article{ padding:64px 0 72px; }
.article .col{ max-width:var(--col); }
.article .kicker{ margin-bottom:18px; }
.article h1{
  font-family:var(--serif); font-weight:600;
  font-size:clamp(2rem,4.6vw,3.1rem); line-height:1.08;
  letter-spacing:-.02em; margin:0 0 18px;
}
.article .standfirst{
  font-size:1.16rem; line-height:1.6; color:var(--ink-soft);
  margin:0 0 26px; max-width:52ch;
}
.meta{
  font-size:13px; color:var(--muted); letter-spacing:.02em;
  padding:16px 0; border-top:1px solid var(--line);
  border-bottom:1px solid var(--line); margin:0 0 40px;
  display:flex; gap:8px 18px; flex-wrap:wrap;
}
.meta b{ color:var(--ink-soft); font-weight:600; }

.article h2{
  font-family:var(--serif); font-weight:600; font-size:24px;
  letter-spacing:-.01em; margin:52px 0 6px;
  display:flex; gap:14px; align-items:baseline;
}
.article h2 .idx{
  font-family:var(--sans); font-size:13px; font-weight:600;
  color:var(--sigg); letter-spacing:.02em; flex:none;
  border:1px solid var(--line); border-radius:50%;
  width:26px; height:26px; line-height:24px; text-align:center;
}
.article h2 + .sub{
  font-size:13.5px; color:var(--muted); margin:0 0 18px;
  padding-left:40px;
}
.article p{ margin:0 0 18px; }
.article figure{ margin:26px 0 10px; }
.article figure img{
  width:100%; border:1px solid var(--line); border-radius:3px;
  background:#fff;
}
.article figcaption{
  font-size:13px; color:var(--muted); line-height:1.55;
  margin-top:12px; max-width:60ch;
}

/* callout / caveat box */
.note{
  background:var(--paper-2); border-left:3px solid var(--sigg);
  border-radius:0 3px 3px 0; padding:22px 26px; margin:40px 0;
}
.note h4{
  font-family:var(--sans); font-size:12.5px; letter-spacing:.14em;
  text-transform:uppercase; color:var(--sigg-dk); margin:0 0 12px;
}
.note ul{ margin:0; padding-left:18px; }
.note li{ font-size:14.5px; color:var(--ink-soft); margin:7px 0; line-height:1.55; }

/* back link */
.back{
  display:inline-flex; align-items:center; gap:8px;
  font-size:14px; color:var(--muted); margin-bottom:12px;
}
.back:hover{ color:var(--sigg); }

/* ---------- footer ---------- */
.site-footer{
  border-top:1px solid var(--line); margin-top:30px;
  padding:40px 0 56px;
}
.foot{ display:flex; justify-content:space-between; gap:28px; flex-wrap:wrap; }
.foot .who{ font-family:var(--serif); font-size:18px; }
.foot .who .dot{
  display:inline-block; width:8px; height:8px; border-radius:50%;
  background:var(--sigg); margin-right:8px;
}
.foot .fine{ font-size:13px; color:var(--muted); line-height:1.7; margin-top:6px; }
.foot .links{ display:flex; gap:22px; flex-wrap:wrap; align-items:flex-start; }
.foot .links a{ font-size:14px; color:var(--ink-soft); }
.foot .links a:hover{ color:var(--sigg); }

/* ---------- 404 ---------- */
.center-page{
  min-height:68vh; display:flex; flex-direction:column;
  justify-content:center; align-items:flex-start; gap:8px;
}
.center-page .big{
  font-family:var(--serif); font-size:clamp(4rem,14vw,9rem);
  line-height:1; color:var(--sigg); letter-spacing:-.03em; margin:0;
}

/* ---------- bilingual ---------- */
.langbar{
  display:flex; align-items:center; gap:14px;
  margin:46px 0 26px; color:var(--muted);
  font-size:11px; letter-spacing:.24em; text-transform:uppercase;
}
.langbar::before,.langbar::after{
  content:""; height:1px; background:var(--line); flex:1;
}
.affil{
  font-size:14.5px; color:var(--muted); letter-spacing:.02em;
  margin:2px 0 24px;
}
.zh-name{
  font-family:var(--serif);
  font-size:1.5rem; letter-spacing:.14em;
  color:var(--ink-soft); margin:-4px 0 10px;
}
.zh-cn{
  font-family:var(--serif);
  color:var(--ink-soft);
  line-height:1.95;
  letter-spacing:.01em;
}
.zh-cn.standfirst{ font-size:1.08rem; line-height:1.9; }
.zh-cn li{ margin:6px 0; }

/* ---------- responsive ---------- */
@media (max-width:760px){
  body{ font-size:16px; }
  .wrap{ padding:0 20px; }
  .hero{ padding:56px 0 44px; }
  .nav{ gap:18px; }
  .nav a{ font-size:13px; }
  .kpis{ grid-template-columns:1fr; gap:18px; }
  .kpi{ display:flex; align-items:baseline; gap:16px; }
  .kpi .num{ font-size:2.3rem; min-width:110px; }
  .kpi .label{ margin-top:0; }
  .cards{ grid-template-columns:1fr; }
  .section-head h2{ font-size:22px; }
  .article h2 .idx{ width:24px; height:24px; line-height:22px; }
  .article h2 + .sub{ padding-left:0; }
  .foot{ flex-direction:column; gap:22px; }
}

@media (prefers-reduced-motion:reduce){
  *{ transition:none !important; animation:none !important; }
}