/* i-Kcal Thermal Academy — design system v1 (2026-08-28)
   Light+dark via prefers-color-scheme; tokens only; Roboto trio; i-Kcal red. */
:root{
  --paper:#FBFBFA; --card:#FFFFFF; --ink:#21262A; --muted:#5A646C;
  --line:#E3E5E4; --soft:#F2F3F1; --accent:#BE1E2D; --accent-ink:#FFFFFF;
  --teal:#0E7C86; --teal-soft:#E4F0F1; --amber:#8A6516; --amber-soft:#F7F0DF;
  --slate:#6B5CA5; --slate-soft:#EDEAF6; --ok:#2E7D32;
  --shadow:0 1px 3px rgba(20,25,30,.07);
}
@media (prefers-color-scheme: dark){
  :root:not([data-theme="light"]){
    --paper:#14171A; --card:#1C2024; --ink:#E7E9EA; --muted:#9AA4AC;
    --line:#2B3137; --soft:#22272C; --accent:#D9515F; --accent-ink:#17191B;
    --teal:#4FB3BC; --teal-soft:#17282B; --amber:#D9B96A; --amber-soft:#2C2618;
    --slate:#9C8FD4; --slate-soft:#242033; --ok:#6FBF73;
    --shadow:none;
  }
}
:root[data-theme="dark"]{
  --paper:#14171A; --card:#1C2024; --ink:#E7E9EA; --muted:#9AA4AC;
  --line:#2B3137; --soft:#22272C; --accent:#D9515F; --accent-ink:#17191B;
  --teal:#4FB3BC; --teal-soft:#17282B; --amber:#D9B96A; --amber-soft:#2C2618;
  --slate:#9C8FD4; --slate-soft:#242033; --ok:#6FBF73;
  --shadow:none;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
@media (prefers-reduced-motion: reduce){ html{scroll-behavior:auto} }
body{
  margin:0; background:var(--paper); color:var(--ink);
  font-family:Roboto,'Segoe UI',system-ui,-apple-system,sans-serif;
  font-size:16.5px; line-height:1.65;
}
h1,h2,h3,h4{font-family:'Roboto Condensed','Arial Narrow',Roboto,sans-serif; line-height:1.15; text-wrap:balance; margin:0 0 10px}
h1{font-size:clamp(30px,5.2vw,44px); font-weight:700}
h2{font-size:25px; font-weight:700; margin-top:40px}
h3{font-size:19px; font-weight:600; margin-top:26px}
p{margin:12px 0}
a{color:var(--teal); text-decoration-thickness:1px; text-underline-offset:2px}
a:hover{color:var(--accent)}
a:focus-visible,button:focus-visible,input:focus-visible,select:focus-visible{outline:2px solid var(--accent); outline-offset:2px; border-radius:4px}
.mono{font-family:'Roboto Mono',Consolas,monospace}
img,svg{max-width:100%}
.container{max-width:1020px; margin:0 auto; padding:0 20px}
.article-body,.prose{max-width:74ch}

/* ---------- header / nav ---------- */
.site-head{border-bottom:1px solid var(--line); background:var(--card); position:sticky; top:0; z-index:40}
.site-head .container{display:flex; align-items:center; gap:18px; height:60px}
.brand{display:flex; align-items:baseline; gap:10px; text-decoration:none; color:var(--ink); white-space:nowrap}
.brand .flame{color:var(--accent); font-family:'Roboto Condensed',sans-serif; font-weight:700; font-size:21px}
.brand .bname{font-family:'Roboto Condensed',sans-serif; font-weight:700; font-size:19px; letter-spacing:.2px}
.brand .btag{display:none; color:var(--muted); font-size:12.5px}
@media(min-width:760px){ .brand .btag{display:inline} }
nav.top{margin-left:auto; display:flex; gap:2px; flex-wrap:wrap}
nav.top a{color:var(--muted); text-decoration:none; font-size:14px; padding:6px 10px; border-radius:8px; font-weight:500}
nav.top a:hover{color:var(--ink); background:var(--soft)}
nav.top a.active{color:var(--accent)}

/* ---------- footer ---------- */
.site-foot{border-top:1px solid var(--line); margin-top:72px; padding:26px 0 40px; color:var(--muted); font-size:13.5px}
.site-foot .container{display:flex; flex-wrap:wrap; gap:8px 26px; justify-content:space-between}
.site-foot a{color:var(--muted)}

/* ---------- chips / badges ---------- */
.chip{font-family:'Roboto Mono',Consolas,monospace; font-size:11.5px; letter-spacing:.06em; padding:3px 10px; border-radius:999px; border:1px solid var(--line); color:var(--muted); background:var(--card); white-space:nowrap}
.chip.level{border-color:var(--accent); color:var(--accent); font-weight:500}
.chip.tool{background:var(--teal-soft); border-color:transparent; color:var(--teal); font-weight:500}
.chip.soon{opacity:.65}
.eyebrow{font-family:'Roboto Mono',Consolas,monospace; font-size:12px; letter-spacing:.14em; text-transform:uppercase; color:var(--accent); font-weight:500}

/* ---------- article header ---------- */
.art-head{padding:40px 0 8px}
.crumb{font-size:13px; color:var(--muted); margin-bottom:14px}
.crumb a{color:var(--muted)}
.lead{font-size:18.5px; color:var(--muted); max-width:66ch; margin-top:8px}
.art-meta{display:flex; gap:8px; flex-wrap:wrap; margin-top:16px}

/* ---------- callouts (the original i-Kcal set) ---------- */
.callout{border:1px solid var(--line); border-left-width:4px; border-radius:0 12px 12px 0; background:var(--card); padding:14px 18px; margin:22px 0; box-shadow:var(--shadow)}
.callout .ct{font-family:'Roboto Mono',Consolas,monospace; font-size:11.5px; letter-spacing:.12em; text-transform:uppercase; font-weight:500; margin-bottom:6px}
.callout p{margin:6px 0; font-size:15px}
.callout ul{margin:6px 0; padding-left:20px}
.callout li{margin:5px 0; font-size:15px}
.callout.pin{border-left-color:var(--accent)} .callout.pin .ct{color:var(--accent)}
.callout.atsite{border-left-color:var(--teal)} .callout.atsite .ct{color:var(--teal)}
.callout.stories{border-left-color:var(--amber); background:var(--amber-soft)} .callout.stories .ct{color:var(--amber)}
.callout.deeper{border-left-color:var(--muted)} .callout.deeper .ct{color:var(--muted)}
.callout.linked{border-left-color:var(--slate)} .callout.linked .ct{color:var(--slate)}

/* ---------- worked example ---------- */
.worked{border:1px solid var(--line); border-radius:12px; background:var(--soft); padding:16px 20px; margin:22px 0}
.worked .wt{font-family:'Roboto Condensed',sans-serif; font-weight:700; font-size:16px; margin-bottom:8px}
.worked p{font-size:15px; margin:7px 0}
.worked .calc{font-family:'Roboto Mono',Consolas,monospace; font-size:13.5px; background:var(--card); border:1px solid var(--line); border-radius:8px; padding:10px 14px; overflow-x:auto; font-variant-numeric:tabular-nums; margin:8px 0; white-space:pre-wrap}

/* ---------- figures / schematic placeholder ---------- */
figure{margin:24px 0}
figcaption{font-size:13px; color:var(--muted); margin-top:8px}
.sch-pending{border:1.5px dashed var(--line); border-radius:12px; padding:26px 20px; text-align:center; color:var(--muted); font-size:14px; background:var(--card)}
.sch-pending .mono{color:var(--accent)}

/* ---------- widgets ---------- */
.widget{border:1px solid var(--line); border-radius:14px; background:var(--card); padding:18px 20px; margin:24px 0; box-shadow:var(--shadow)}
.widget .wtitle{font-family:'Roboto Condensed',sans-serif; font-weight:700; font-size:17px; margin-bottom:12px}
.widget .wnote{font-size:12px; color:var(--muted); margin-top:12px}
.wrow{display:flex; flex-wrap:wrap; gap:10px; align-items:center; margin:10px 0}
.wrow label{font-size:13.5px; color:var(--muted); min-width:112px}
.widget input[type=number],.widget select{
  font:inherit; font-size:15px; color:var(--ink); background:var(--paper);
  border:1px solid var(--line); border-radius:8px; padding:7px 10px; max-width:130px;
  font-variant-numeric:tabular-nums;
}
.widget input[type=range]{flex:1 1 180px; accent-color:var(--accent)}
.wout{display:grid; grid-template-columns:repeat(auto-fit,minmax(128px,1fr)); gap:10px; margin-top:12px}
.wcell{background:var(--soft); border:1px solid var(--line); border-radius:10px; padding:9px 12px}
.wcell .k{font-size:11.5px; color:var(--muted); letter-spacing:.04em}
.wcell .v{font-family:'Roboto Mono',Consolas,monospace; font-size:16.5px; font-variant-numeric:tabular-nums; margin-top:2px}
.wcell .u{font-size:11.5px; color:var(--muted)}
.seg{display:inline-flex; border:1px solid var(--line); border-radius:8px; overflow:hidden}
.seg button{font:inherit; font-size:13px; padding:6px 12px; border:0; background:var(--card); color:var(--muted); cursor:pointer}
.seg button.on{background:var(--accent); color:var(--accent-ink)}
.svgwrap{overflow-x:auto}
.svgwrap svg text{font-family:Roboto,'Segoe UI',sans-serif}

/* ---------- tables ---------- */
.tblwrap{overflow-x:auto; border:1px solid var(--line); border-radius:12px; background:var(--card); margin:20px 0}
table{border-collapse:collapse; width:100%; font-size:14.5px; min-width:560px}
th{font-family:'Roboto Mono',Consolas,monospace; font-size:11.5px; letter-spacing:.08em; text-transform:uppercase; text-align:left; color:var(--muted); font-weight:500; padding:11px 14px; border-bottom:1px solid var(--line); background:var(--soft)}
td{padding:10px 14px; border-bottom:1px solid var(--line); vertical-align:top; font-variant-numeric:tabular-nums}
tr:last-child td{border-bottom:none}

/* ---------- go deeper / footer of article ---------- */
.godeeper{margin-top:40px; border-top:2px solid var(--accent); padding-top:18px}
.godeeper h2{margin-top:0; font-size:21px}
.gditems{display:grid; grid-template-columns:repeat(auto-fit,minmax(230px,1fr)); gap:12px; margin-top:12px}
.gd{border:1px solid var(--line); border-radius:12px; background:var(--card); padding:13px 15px; text-decoration:none; color:var(--ink); display:block}
.gd:hover{border-color:var(--teal)}
.gd .gk{display:block; font-family:'Roboto Mono',Consolas,monospace; font-size:11px; letter-spacing:.1em; text-transform:uppercase; color:var(--muted)}
.gd .gt{display:block; font-weight:500; font-size:15px; margin-top:4px; color:var(--ink)}
.art-foot{color:var(--muted); font-size:13px; margin-top:34px}

/* ---------- home / hub ---------- */
.hero{padding:64px 0 30px}
.hero .tagline{font-family:'Roboto Condensed',sans-serif; font-size:clamp(20px,3vw,26px); color:var(--accent); font-weight:600; margin-top:4px}
.hero .sub{font-size:18px; color:var(--muted); max-width:64ch; margin-top:14px}
.cta{display:inline-block; margin-top:22px; background:var(--accent); color:var(--accent-ink); text-decoration:none; font-weight:500; padding:11px 22px; border-radius:10px; font-size:15.5px}
.cta:hover{filter:brightness(1.08); color:var(--accent-ink)}
.cta.ghost{background:transparent; color:var(--teal); border:1px solid var(--teal); margin-left:10px}
.fgrid{display:grid; grid-template-columns:repeat(auto-fit,minmax(280px,1fr)); gap:16px; margin:26px 0}
.fcard{border:1px solid var(--line); border-radius:14px; background:var(--card); padding:20px 22px; text-decoration:none; color:var(--ink); display:flex; flex-direction:column; gap:8px; box-shadow:var(--shadow)}
.fcard:hover{border-color:var(--accent)}
.fcard h3{margin:0; font-size:19px}
.fcard .fb{color:var(--muted); font-size:14px; flex:1}
.fcard .fmeta{display:flex; gap:8px; flex-wrap:wrap}
.lessonlist{list-style:none; padding:0; margin:18px 0; display:grid; gap:10px}
.lessonlist li{border:1px solid var(--line); border-radius:12px; background:var(--card)}
.lessonlist a,.lessonlist .soonrow{display:block; padding:13px 16px; text-decoration:none; color:var(--ink)}
.lessonlist a:hover{background:var(--soft); border-radius:12px}
.lessonlist .lrow{display:flex; gap:14px; align-items:baseline}
.lessonlist .lid{font-family:'Roboto Mono',Consolas,monospace; font-size:12px; color:var(--accent); min-width:30px}
.lessonlist .lt{font-weight:500; flex:1}
.lessonlist .ldsc{display:block; color:var(--muted); font-size:13.5px; line-height:1.5; margin-top:4px; padding-left:44px}
@media(max-width:560px){ .lessonlist .ldsc{padding-left:0} }
.lessonlist .soonrow{color:var(--muted)}
.lessonlist .soonrow .lid{color:var(--muted)}
.strip{border:1px solid var(--line); border-radius:14px; background:var(--card); padding:18px 22px; margin:30px 0}
.strip h2{margin-top:0; font-size:21px}
.toolchips{display:flex; flex-wrap:wrap; gap:8px; margin-top:10px}
.notebox{border-left:4px solid var(--teal); background:var(--soft); border-radius:0 10px 10px 0; padding:12px 16px; font-size:14px; color:var(--muted); margin:20px 0}

/* ---------- glossary ---------- */
dl.gloss{max-width:74ch}
dl.gloss dt{font-weight:700; font-family:'Roboto Condensed',sans-serif; font-size:17px; margin-top:18px}
dl.gloss dd{margin:4px 0 0 0; color:var(--ink)}
dl.gloss dd .also{color:var(--muted); font-size:13.5px}

@media(max-width:640px){
  body{font-size:16px}
  .art-head{padding-top:26px}
  .hero{padding-top:36px}
}

/* ---------- reader UX kit (v2, 2026-08-28) ---------- */
h2{scroll-margin-top:76px}
h3{scroll-margin-top:76px}
.article-body{font-size:17px; line-height:1.7}
.article-body>p:first-child{font-size:17.5px}

.readbar{position:fixed; top:0; left:0; right:0; height:3px; z-index:60; pointer-events:none}
.readbar div{height:100%; width:0; background:var(--accent)}

.theme-btn{margin-left:8px; width:34px; height:34px; flex:0 0 auto; display:inline-flex; align-items:center; justify-content:center; border:1px solid var(--line); border-radius:9px; background:var(--card); color:var(--muted); cursor:pointer; padding:0}
.theme-btn:hover{color:var(--ink); border-color:var(--muted)}

.totop{position:fixed; right:18px; bottom:18px; width:42px; height:42px; border-radius:12px; border:1px solid var(--line); background:var(--card); color:var(--muted); cursor:pointer; display:flex; align-items:center; justify-content:center; opacity:0; visibility:hidden; transition:opacity .2s, visibility .2s; z-index:50; box-shadow:var(--shadow)}
.totop.on{opacity:1; visibility:visible}
.totop:hover{color:var(--accent); border-color:var(--accent)}

.toc{border:1px solid var(--line); border-left:4px solid var(--accent); border-radius:0 12px 12px 0; background:var(--card); padding:14px 18px; margin:22px 0 8px; max-width:74ch}
.toc .toct{font-family:'Roboto Mono',Consolas,monospace; font-size:11.5px; letter-spacing:.12em; text-transform:uppercase; color:var(--muted); margin-bottom:6px}
.toc ol{margin:0; padding-left:20px; columns:2; column-gap:30px}
.toc li{font-size:14.5px; margin:4px 0; break-inside:avoid}
.toc a{color:var(--ink); text-decoration:none}
.toc a:hover{color:var(--accent)}
@media(max-width:640px){ .toc ol{columns:1} }

.pn{display:grid; grid-template-columns:1fr 1fr; gap:12px; margin-top:26px}
@media(max-width:560px){ .pn{grid-template-columns:1fr} }
.pn a{border:1px solid var(--line); border-radius:12px; background:var(--card); padding:13px 15px; text-decoration:none; color:var(--ink); display:block}
.pn a:hover{border-color:var(--accent)}
.pn .pnk{display:block; font-family:'Roboto Mono',Consolas,monospace; font-size:11px; letter-spacing:.1em; text-transform:uppercase; color:var(--muted)}
.pn .pnt{display:block; font-weight:500; font-size:15px; margin-top:4px}
.pn a.next{text-align:right}

/* mobile header: brand + theme button on row 1, nav on row 2 */
@media(max-width:700px){
  .site-head .container{height:auto; flex-wrap:wrap; padding-top:8px; padding-bottom:6px; gap:2px 8px}
  .brand{flex:1 1 auto}
  .theme-btn{order:2; margin-left:auto; width:32px; height:32px}
  nav.top{order:3; width:100%; margin-left:0; gap:0; justify-content:flex-start}
  nav.top a{font-size:13.5px; padding:4px 10px 4px 0}
}