/* Energy in Steel — layout: sticky top bar, single readable column, tools as two-pane labs */
:root{
  --bg:#f3f3f2; --panel:#ffffff; --ink:#2e2f31; --ink2:#55575b; --mute:#7d7f84; --line:#dedfdf; --soft:#ecedec;
  --red:#d8180f; --fuel:#d9760a; --air:#2a74b5; --ok:#1d7f46; --warn:#b98300; --bad:#c62a1f;
  --shade-bad:rgba(228,27,18,.09); --shade-warn:rgba(217,154,0,.12); --shade-ok:rgba(31,138,76,.08);
  --hero:#26272a; --hero-ink:#f3f3f2; --hero-mute:#b9bbbf;
  --f-display:"Barlow Semi Condensed","Arial Narrow","Noto Sans",Calibri,"Segoe UI",sans-serif;
  --f-body:"Source Sans 3","Noto Sans","Noto Sans Devanagari","Noto Sans SC","Noto Sans JP","PingFang SC","Hiragino Sans","Microsoft YaHei",Calibri,"Segoe UI",Arial,sans-serif;
  color-scheme:light;
}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]){
  --bg:#1b1c1e; --panel:#242528; --ink:#ededee; --ink2:#c4c5c8; --mute:#94969b; --line:#3a3b3f; --soft:#2d2e32;
  --red:#ff5a4d; --fuel:#f59b36; --air:#5aa4e6; --ok:#43b872; --warn:#e7b43a; --bad:#ff5b4f;
  --shade-bad:rgba(255,74,61,.15); --shade-warn:rgba(231,180,58,.15); --shade-ok:rgba(67,184,114,.12);
  --hero:#121314; --hero-ink:#f3f3f2; --hero-mute:#a7a9ad; color-scheme:dark;}}
:root[data-theme="dark"]{
  --bg:#1b1c1e; --panel:#242528; --ink:#ededee; --ink2:#c4c5c8; --mute:#94969b; --line:#3a3b3f; --soft:#2d2e32;
  --red:#ff5a4d; --fuel:#f59b36; --air:#5aa4e6; --ok:#43b872; --warn:#e7b43a; --bad:#ff5b4f;
  --shade-bad:rgba(255,74,61,.15); --shade-warn:rgba(231,180,58,.15); --shade-ok:rgba(67,184,114,.12);
  --hero:#121314; --hero-ink:#f3f3f2; --hero-mute:#a7a9ad; color-scheme:dark;}

*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--bg);color:var(--ink);font:16px/1.55 var(--f-body)}
a{color:var(--air)}
:focus-visible{outline:2px solid var(--air);outline-offset:2px}
.gutter{padding-left:max(16px,env(safe-area-inset-left,0px));padding-right:max(16px,env(safe-area-inset-right,0px))}
.wrap{max-width:1240px;margin:0 auto}

/* ---------- top bar ---------- */
body::before{content:"";position:fixed;inset:0 0 auto;height:env(safe-area-inset-top,0px);z-index:30;background:var(--panel)}
.topbar{position:sticky;top:env(safe-area-inset-top,0px);z-index:20;background:var(--panel);border-bottom:1px solid var(--line)}
.topbar .wrap{display:flex;align-items:center;gap:14px;min-height:56px;flex-wrap:wrap}
.logo{display:flex;align-items:center;gap:9px;text-decoration:none;color:var(--ink);font:700 19px/1 var(--f-display);letter-spacing:.2px;margin-right:auto}
.logo svg{width:26px;height:26px;flex-shrink:0}
.logo span b{color:var(--red);font-weight:700}
.mainnav{display:flex;gap:2px;flex-wrap:wrap}
.mainnav a{font:600 15px var(--f-display);letter-spacing:.3px;color:var(--ink2);text-decoration:none;padding:7px 10px;border-radius:6px}
.mainnav a:hover,.mainnav a[aria-current="page"]{background:var(--soft);color:var(--ink)}
.langsel{position:relative}
.langsel summary{list-style:none;cursor:pointer;font:600 14px var(--f-body);color:var(--ink2);border:1px solid var(--line);border-radius:6px;padding:6px 10px;display:flex;align-items:center;gap:6px}
.langsel summary::-webkit-details-marker{display:none}
.langsel summary svg{width:16px;height:16px}
.langsel ul{position:absolute;right:0;top:calc(100% + 6px);margin:0;padding:6px;list-style:none;background:var(--panel);border:1px solid var(--line);border-radius:8px;box-shadow:0 8px 24px rgba(0,0,0,.14);min-width:170px;z-index:25}
.langsel li a{display:flex;justify-content:space-between;gap:12px;padding:7px 10px;border-radius:5px;text-decoration:none;color:var(--ink);font-size:14.5px}
.langsel li a:hover{background:var(--soft)}
.langsel li a small{color:var(--mute);text-transform:uppercase;font-size:11.5px;letter-spacing:.5px}
.langsel li a[aria-current="true"]{background:var(--soft);font-weight:700}
.stripe{height:4px;background:linear-gradient(90deg,var(--air),var(--fuel) 50%,var(--red))}

/* ---------- ads ---------- */
.adbox{margin:18px auto;max-width:1240px;text-align:center}
.adbox .adlabel{display:block;font:600 10.5px var(--f-body);text-transform:uppercase;letter-spacing:.8px;color:var(--mute);margin-bottom:4px}
.adbox.placeholder .adfill{border:1px dashed var(--line);border-radius:8px;min-height:90px;display:flex;align-items:center;justify-content:center;color:var(--mute);font-size:13px;background:var(--panel)}

/* ---------- home ---------- */
.hero{background:var(--hero);color:var(--hero-ink);position:relative;overflow:hidden}
.hero .wrap{position:relative;z-index:1;padding-block:44px 40px;display:grid;grid-template-columns:minmax(0,1.25fr) minmax(0,1fr);gap:32px;align-items:center}
@media (max-width:860px){.hero .wrap{grid-template-columns:1fr;padding-block:30px 26px}}
.eyebrow{font:600 12.5px var(--f-body);text-transform:uppercase;letter-spacing:1.2px;color:var(--fuel)}
.hero h1{font:700 clamp(32px,5.4vw,54px)/1.04 var(--f-display);margin:10px 0 14px;text-wrap:balance;letter-spacing:.2px}
.hero h1 span{color:var(--fuel)}
.hero p{color:var(--hero-mute);font-size:17px;max-width:600px;margin:0 0 22px}
.btn{display:inline-flex;align-items:center;gap:8px;font:600 16px var(--f-display);letter-spacing:.3px;padding:11px 18px;border-radius:7px;text-decoration:none;background:var(--red);color:#fff}
.btn:hover{filter:brightness(1.08)}
.hero-figure{background:#1a1b1d;border:1px solid #3a3b3f;border-radius:10px;padding:10px;min-width:0}
.hero-figure canvas{width:100%;height:220px;display:block;border-radius:6px}
.hero-figure .cap{display:flex;justify-content:space-between;gap:8px;color:#a7a9ad;font-size:12.5px;margin-top:8px;font-variant-numeric:tabular-nums;flex-wrap:wrap}
.hero-figure .cap b{color:#f59b36;font-family:var(--f-display);font-size:15px}
.home-sec{padding-block:38px 6px}
.home-sec h2{font:700 26px/1.15 var(--f-display);margin:0 0 4px;text-wrap:balance}
.home-sec .sub{color:var(--mute);margin:0 0 18px}
.toolgrid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:16px}
@media (max-width:760px){.toolgrid{grid-template-columns:1fr}}
.toolcard{background:var(--panel);border:1px solid var(--line);border-radius:10px;padding:20px;display:flex;flex-direction:column;gap:10px;text-decoration:none;color:var(--ink);transition:border-color .15s}
.toolcard:hover{border-color:var(--ink2)}
.toolcard .tags{display:flex;gap:6px;flex-wrap:wrap}
.toolcard .tags span{font:600 11.5px var(--f-body);text-transform:uppercase;letter-spacing:.6px;color:var(--ink2);background:var(--soft);border-radius:99px;padding:3px 9px}
.toolcard h3{font:700 22px/1.15 var(--f-display);margin:0}
.toolcard p{margin:0;color:var(--ink2);font-size:15px}
.toolcard .go{margin-top:auto;font:600 15px var(--f-display);color:var(--red);letter-spacing:.3px}
.toolcard .formula{font:600 14px var(--f-display);color:var(--mute);font-variant-numeric:tabular-nums}
.nextlist{list-style:none;margin:0;padding:0;display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:0 24px}
@media (max-width:760px){.nextlist{grid-template-columns:1fr}}
.nextlist li{padding:11px 0;border-bottom:1px solid var(--line);color:var(--ink2);display:flex;gap:10px;align-items:baseline}
.nextlist li::before{content:"";width:8px;height:8px;border-radius:50%;border:2px solid var(--fuel);flex-shrink:0;transform:translateY(-1px)}
.authorbox{display:grid;grid-template-columns:auto minmax(0,1fr);gap:18px;align-items:start;background:var(--panel);border:1px solid var(--line);border-radius:10px;padding:20px}
.authorbox .mono{width:54px;height:54px;border-radius:50%;background:var(--hero);color:var(--fuel);display:flex;align-items:center;justify-content:center;font:700 22px var(--f-display)}
.authorbox p{margin:4px 0 0;color:var(--ink2);max-width:70ch}
.authorbox h3{margin:0;font:700 19px var(--f-display)}

/* ---------- article / legal ---------- */
.prose{max-width:760px;padding-block:34px 10px}
.prose h1{font:700 clamp(30px,4.5vw,40px)/1.1 var(--f-display);margin:0 0 14px;text-wrap:balance}
.prose h2{font:700 22px/1.2 var(--f-display);margin:28px 0 6px}
.prose p,.prose li{color:var(--ink2);font-size:16.2px}
.prose .meta{color:var(--mute);font-size:14px}

/* ---------- tool pages (from the original labs) ---------- */
.lab{padding-block:10px 20px}
.crumbs{font-size:13.5px;color:var(--mute);padding-top:18px}
.crumbs a{color:var(--mute)}
header.top{padding-block:10px 6px}
.brand h1{font:700 32px/1.1 var(--f-display);letter-spacing:.2px;margin:0;text-wrap:balance}
.brand h1 span{color:var(--red)}
.brand p{margin:6px 0 0;color:var(--ink2);font-size:15.5px;max-width:800px}
.labstripe{height:4px;background:linear-gradient(90deg,var(--air),var(--fuel) 50%,var(--red));border-radius:2px;margin:12px 0 18px}
nav.tabs{position:sticky;top:calc(env(safe-area-inset-top,0px) + 57px);z-index:5;display:flex;gap:4px;overflow-x:auto;background:var(--bg);border-bottom:1px solid var(--line);margin-bottom:26px;padding-block:4px;scrollbar-width:thin}
nav.tabs a{font:600 15px var(--f-display);letter-spacing:.3px;color:var(--ink2);text-decoration:none;padding:8px 12px;border-radius:6px;white-space:nowrap}
nav.tabs a:hover{background:var(--soft);color:var(--ink)}
nav.tabs a span{color:var(--mute);margin-right:5px}
@media (max-width:760px){nav.tabs{top:0;position:relative}}
section.lab-sec{margin-bottom:44px;scroll-margin-top:120px}
.lab h2{font:700 24px/1.2 var(--f-display);margin:0 0 6px;text-wrap:balance}
.lab h2 small{display:block;font:500 14px var(--f-body);color:var(--mute);margin-top:3px}
.lead{color:var(--ink2);font-size:15.3px;max-width:840px;margin:0 0 20px}
.cards3{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px}
@media (max-width:860px){.cards3{grid-template-columns:1fr}}
.card{background:var(--panel);border:1px solid var(--line);border-radius:10px;padding:18px 20px;min-width:0}
.card h3{font:700 18px var(--f-display);margin:0 0 8px;display:flex;align-items:center;gap:8px}
.card h3 i.dot{width:12px;height:12px;border-radius:50%;display:inline-block;flex-shrink:0}
.card p{margin:0 0 8px;font-size:14.5px;color:var(--ink2)}
.card .tag{display:inline-block;font:600 12.5px var(--f-body);color:var(--panel);background:var(--mute);border-radius:99px;padding:3px 10px;margin-top:4px}
.panel2{display:grid;grid-template-columns:350px minmax(0,1fr);gap:20px;align-items:start}
@media (max-width:980px){.panel2{grid-template-columns:1fr}}
.ctrl{background:var(--panel);border:1px solid var(--line);border-radius:10px;padding:18px;display:flex;flex-direction:column;gap:14px;min-width:0}
.ctrl h3{font:700 17px var(--f-display);margin:4px 0 0;color:var(--ink2);border-top:1px solid var(--line);padding-top:12px;display:flex;justify-content:space-between;align-items:center;gap:8px}
.ctrl h3.first{border-top:0;padding-top:0;margin-top:0}
.f{display:flex;flex-direction:column;gap:4px}
.f label,.f .lbl{display:flex;justify-content:space-between;gap:8px;font-size:13.5px;color:var(--ink2)}
.f label output{font:600 14.5px var(--f-display);color:var(--ink);font-variant-numeric:tabular-nums;white-space:nowrap}
input[type=range]{width:100%;accent-color:var(--red)}
select{font:15px var(--f-body);padding:7px 8px;border:1px solid var(--line);border-radius:6px;background:var(--panel);color:var(--ink);width:100%}
.seg{display:flex;border:1px solid var(--line);border-radius:6px;overflow:hidden}
.seg button{flex:1;font:600 12.5px var(--f-body);padding:7px 5px;border:0;background:var(--panel);color:var(--ink2);cursor:pointer}
.seg button+button{border-left:1px solid var(--line)}
.seg button[aria-pressed="true"]{background:var(--ink);color:var(--panel)}
.total-badge{font:600 12.5px var(--f-display);padding:3px 9px;border-radius:99px;display:inline-block}
.total-ok{background:var(--shade-ok);color:var(--ok)}
.total-bad{background:var(--shade-bad);color:var(--bad)}
.main2{display:flex;flex-direction:column;gap:16px;min-width:0}
.kpis{display:grid;grid-template-columns:repeat(auto-fit,minmax(150px,1fr));gap:10px}
.kpi{background:var(--panel);border:1px solid var(--line);border-radius:8px;padding:11px 13px;min-width:0}
.kpi .l{font-size:11.5px;color:var(--mute);text-transform:uppercase;letter-spacing:.5px}
.kpi .v{font:700 25px/1.15 var(--f-display);font-variant-numeric:tabular-nums}
.kpi .s{font-size:12px;color:var(--ink2)}
.kpi.hi{border-color:var(--red);background:var(--shade-bad)}
.kpi.hib{border-color:var(--air);background:var(--shade-ok)}
.furnace-card{background:var(--panel);border:1px solid var(--line);border-radius:10px;padding:14px}
.furnace-card h3,.chart-h{font:600 16px var(--f-display);color:var(--ink2);margin:0 0 8px}
canvas#furnace{width:100%;height:360px;display:block;border-radius:8px}
@media (max-width:600px){canvas#furnace{height:260px}}
canvas.ch{width:100%;height:230px;display:block}
.legend{display:flex;gap:14px;flex-wrap:wrap;font-size:13px;color:var(--ink2);margin-top:6px}
.legend i{display:inline-block;width:16px;height:10px;vertical-align:middle;margin-right:5px;border-radius:2px}
.steps{background:var(--soft);border-radius:8px;padding:14px 16px;font-size:13.8px;line-height:1.75;font-variant-numeric:tabular-nums;overflow-x:auto}
.steps b{color:var(--red)}
.obs{background:var(--soft);border-radius:8px;padding:14px 16px;font-size:14.5px}
.obs > b{font-family:var(--f-display);letter-spacing:.3px}
.obs ul{margin:6px 0 0;padding-left:18px}
.formula-box{background:var(--panel);border:1px solid var(--line);border-radius:10px;padding:22px 20px;text-align:center;overflow-x:auto}
.formula-box .big{font:700 clamp(17px,2.6vw,24px)/1.4 var(--f-display);color:var(--ink)}
.formula-box .big sub{font-size:.6em}
.tblwrap{overflow-x:auto;border:1px solid var(--line);border-radius:10px}
.tbl{width:100%;border-collapse:collapse;font-size:13.3px;background:var(--panel)}
.tbl td,.tbl th{padding:7px 9px;border-bottom:1px solid var(--line)}
.tbl.num td,.tbl.num th{text-align:right}
.tbl td:first-child,.tbl th:first-child{text-align:left}
.tbl th{font:600 11.5px var(--f-display);color:var(--mute);text-transform:uppercase;letter-spacing:.4px;background:var(--soft)}
.tbl tr:last-child td{border-bottom:0}
.tbl tr.hl td{font-weight:700;background:var(--shade-warn)}
.tbl input{width:64px;font:600 13px var(--f-body);text-align:right;padding:4px 5px;border:1px solid var(--line);border-radius:5px;background:var(--panel);color:var(--ink);font-variant-numeric:tabular-nums}
.tbl input.err{border-color:var(--bad);background:var(--shade-bad)}
.tbl td.mixcell{background:var(--shade-ok);font-weight:700;font-variant-numeric:tabular-nums}
.tbl.ref td{font-size:14.3px;padding:10px 12px}
.tbl-actions{display:flex;justify-content:flex-end;margin-bottom:10px}
.btn-reset{font:600 13px var(--f-body);padding:7px 12px;border-radius:6px;border:1px solid var(--line);background:var(--panel);color:var(--ink2);cursor:pointer}
.btn-reset:hover{background:var(--soft);color:var(--ink)}
.note{font-size:12.3px;color:var(--mute);margin-top:6px}
.sphere-wrap{display:flex;align-items:center;justify-content:center}
.sphere{display:flex;flex-direction:column;align-items:center;justify-content:center;border-radius:50%;width:150px;height:150px;box-shadow:inset -14px -14px 30px rgba(0,0,0,.18),0 6px 16px rgba(0,0,0,.15);color:#fff;font:700 15px var(--f-display);text-align:center;padding:10px}
.sphere small{display:block;font:500 11.5px var(--f-body);opacity:.92}

/* ---------- footer ---------- */
footer.site{margin-top:40px;border-top:1px solid var(--line);background:var(--panel)}
footer.site .wrap{padding-block:26px 30px;display:grid;grid-template-columns:minmax(0,1.4fr) minmax(0,1fr);gap:24px}
@media (max-width:760px){footer.site .wrap{grid-template-columns:1fr}}
footer.site p{margin:0 0 8px;color:var(--mute);font-size:13.3px;max-width:62ch}
footer.site nav{display:flex;flex-direction:column;gap:6px;align-items:flex-start}
footer.site nav a{color:var(--ink2);font-size:14px;text-decoration:none}
footer.site nav a:hover{color:var(--ink);text-decoration:underline}

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

/* ---------- author page ---------- */
.au-hero{background:var(--hero);color:var(--hero-ink)}
.au-hero .wrap{padding-block:4px 34px}
.au-hero .crumbs,.au-hero .crumbs a{color:var(--hero-mute)}
.au-head{display:flex;gap:22px;align-items:center;margin-top:18px;flex-wrap:wrap}
.au-mono{width:96px;height:96px;border-radius:50%;flex-shrink:0;display:flex;align-items:center;justify-content:center;font:700 38px var(--f-display);color:var(--hero);background:linear-gradient(135deg,#f59b36,#e8820f 55%,#d8180f);letter-spacing:1px}
.au-id{min-width:0;flex:1}
.au-id h1{font:700 clamp(30px,5vw,46px)/1.05 var(--f-display);margin:6px 0 6px;text-wrap:balance}
.au-role{margin:0;font:600 18px var(--f-display);color:#f59b36;letter-spacing:.2px}
.au-loc{margin:2px 0 0;color:var(--hero-mute);font-size:14.5px}
.au-actions{display:flex;gap:10px;flex-wrap:wrap;margin-top:14px}
.btn.ghost{background:transparent;border:1px solid #55575b;color:var(--hero-ink);font-family:var(--f-body);font-size:14.5px;overflow-wrap:anywhere}
.au-intro{max-width:760px;color:var(--hero-mute);font-size:17px;margin:22px 0 0}
.au-stats{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:0;margin:26px 0 0;border-top:1px solid #3a3b3f}
@media (max-width:640px){.au-stats{grid-template-columns:1fr}}
.au-stats div{padding:14px 18px 0 0}
.au-stats dt{font:700 34px/1 var(--f-display);color:var(--hero-ink);font-variant-numeric:tabular-nums}
.au-stats dd{margin:6px 0 0;color:var(--hero-mute);font-size:14px;max-width:30ch}
.au-grid{display:grid;grid-template-columns:minmax(0,1.5fr) minmax(0,1fr);gap:32px;padding-block:34px 10px;align-items:start}
@media (max-width:900px){.au-grid{grid-template-columns:1fr}}
.au-block h2{font:700 22px/1.2 var(--f-display);margin:26px 0 8px}
.au-block h2:first-child{margin-top:0}
.au-block p{color:var(--ink2);font-size:16.2px;margin:0;max-width:68ch}
.au-tags{list-style:none;margin:0;padding:0;display:flex;flex-wrap:wrap;gap:8px}
.au-tags li{background:var(--panel);border:1px solid var(--line);border-radius:99px;padding:6px 12px;font-size:14px;color:var(--ink)}
.au-side{display:flex;flex-direction:column;gap:14px;min-width:0}
.au-card{background:var(--panel);border:1px solid var(--line);border-radius:10px;padding:18px 20px}
.au-card h3{font:700 13px var(--f-body);text-transform:uppercase;letter-spacing:.8px;color:var(--mute);margin:0 0 12px}
.au-card p{margin:0 0 6px;color:var(--ink2);font-size:15px}
.au-list{list-style:none;margin:0;padding:0;display:flex;flex-direction:column;gap:14px}
.au-list li{display:flex;flex-direction:column;gap:3px;padding-left:12px;border-left:3px solid var(--fuel)}
.au-list b{font-weight:700;font-size:15px;line-height:1.35}
.au-list span{color:var(--ink2);font-size:13.8px}
.au-list a{font-size:13.8px;overflow-wrap:anywhere}