:root{
  --bg:#F2F5F2; --surface:#FFFFFF; --field:#F7F9F7; --ink:#15211B; --muted:#5A6A61; --line:#D4DDD7;
  --mask:#1D5640; --mask-ink:#EEF5F0; --mask-dim:#9CC2AE;
  --copper:#A35C22; --copper-soft:#F6EADF; --copper-line:#E6CDB6;
  --warn:#9A3B1E; --warn-bg:#FBE9E2; --ok:#1F6B45;
  --sans:"IBM Plex Sans KR",system-ui,-apple-system,"Apple SD Gothic Neo","Malgun Gothic",sans-serif;
  --mono:"IBM Plex Mono",ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
}
@media (prefers-color-scheme: dark){
  :root:not([data-theme="light"]){
    color-scheme:dark;
    --bg:#0C1511; --surface:#131F19; --field:#0F1914; --ink:#E2EBE5; --muted:#92A499; --line:#26362D;
    --mask:#17442F; --mask-ink:#E4F0E9; --mask-dim:#7FA893;
    --copper:#E0A06A; --copper-soft:#261C14; --copper-line:#4A3522;
    --warn:#F0A48A; --warn-bg:#2C1A14; --ok:#7FD0A2;
  }
}
:root[data-theme="dark"]{
  color-scheme:dark;
  --bg:#0C1511; --surface:#131F19; --field:#0F1914; --ink:#E2EBE5; --muted:#92A499; --line:#26362D;
  --mask:#17442F; --mask-ink:#E4F0E9; --mask-dim:#7FA893;
  --copper:#E0A06A; --copper-soft:#261C14; --copper-line:#4A3522;
  --warn:#F0A48A; --warn-bg:#2C1A14; --ok:#7FD0A2;
}
*{box-sizing:border-box}
body{background:var(--bg);color:var(--ink);font-family:var(--sans);font-size:15px;line-height:1.6}
.wrap{max-width:1120px;margin:0 auto;padding-inline:16px}

/* header: solder mask board */
.board{background:var(--mask);color:var(--mask-ink);
  background-image:radial-gradient(circle at 1px 1px, rgba(255,255,255,.07) 1px, transparent 1.5px);
  background-size:18px 18px;border-bottom:3px solid var(--copper)}
.board .wrap{padding-block:28px 26px;display:flex;flex-wrap:wrap;align-items:flex-end;justify-content:space-between;gap:12px 24px}
.brand h1{margin:0;font-size:clamp(26px,4vw,34px);font-weight:700;letter-spacing:-.01em;text-wrap:balance}
.brand p{margin:4px 0 0;color:var(--mask-dim);font-size:14px;max-width:46ch}
.silk{font-family:var(--mono);font-size:11px;letter-spacing:.12em;text-transform:uppercase;color:var(--mask-dim);display:flex;gap:14px;flex-wrap:wrap}
.silk b{color:var(--mask-ink);font-weight:500}

.hint{font-size:13px;color:var(--muted);padding-block:14px 0}
.hint code{font-family:var(--mono);background:var(--surface);border:1px solid var(--line);border-radius:4px;padding:0 5px;color:var(--ink)}

.layout{display:grid;grid-template-columns:minmax(0,1fr);gap:20px;padding-block:14px 48px}
main{min-width:0}
@media (min-width:880px){.layout{grid-template-columns:210px minmax(0,1fr);gap:28px}}

/* nav */
nav.list{overflow-x:auto}
nav.list ul{list-style:none;margin:0;padding:0;display:flex;gap:6px}
@media (min-width:880px){nav.list{position:sticky;top:calc(env(safe-area-inset-top,0px) + 16px);align-self:start}
  nav.list ul{flex-direction:column}}
nav.list a{display:flex;align-items:center;gap:10px;padding:8px 12px;border-radius:8px;color:var(--ink);text-decoration:none;white-space:nowrap;font-size:14px;border:1px solid transparent}
nav.list a .ref{font-family:var(--mono);font-size:11px;color:var(--muted);min-width:2.6em;letter-spacing:.04em}
nav.list a:hover{background:var(--surface);border-color:var(--line)}
nav.list a[aria-current="page"]{background:var(--surface);border-color:var(--line);font-weight:600}
nav.list a[aria-current="page"] .ref{color:var(--copper)}
nav.list a:focus-visible,button:focus-visible,input:focus-visible,select:focus-visible,textarea:focus-visible{outline:2px solid var(--copper);outline-offset:2px}

/* calc panel */
.calc{background:var(--surface);border:1px solid var(--line);border-radius:10px;padding:22px clamp(16px,3vw,28px) 26px}
.calc header{display:flex;align-items:baseline;gap:12px;flex-wrap:wrap}
.calc h2{margin:0;font-size:22px;font-weight:700;letter-spacing:-.01em;text-wrap:balance}
.calc header .ref{font-family:var(--mono);font-size:12px;color:var(--copper);letter-spacing:.08em}
.calc .lede{margin:6px 0 18px;color:var(--muted);max-width:62ch}
.grid{display:grid;gap:20px}
@media (min-width:720px){.grid{grid-template-columns:minmax(0,1fr) minmax(0,1fr)}}
.fields{display:grid;grid-template-columns:minmax(0,1fr);gap:12px;align-content:start}
.grid>*{min-width:0}
select.plain{max-width:100%}
.row2{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px}
label.f,.inp{min-width:0}
label.f{display:grid;gap:4px;font-size:13px;color:var(--muted)}
.inp{display:flex;align-items:center;background:var(--field);border:1px solid var(--line);border-radius:7px}
.inp:focus-within{border-color:var(--copper)}
.inp input,.inp select{flex:1;min-width:0;border:0;background:transparent;color:var(--ink);font-family:var(--mono);font-size:15px;padding:9px 10px}
.inp input:focus,.inp select:focus{outline:none}
.inp .u{font-family:var(--mono);font-size:13px;color:var(--muted);padding-right:10px}
select.plain{width:100%;font-family:var(--sans);font-size:14px;background:var(--field);color:var(--ink);border:1px solid var(--line);border-radius:7px;padding:9px 10px}
textarea{width:100%;min-height:92px;resize:vertical;font-family:var(--mono);font-size:15px;background:var(--field);color:var(--ink);border:1px solid var(--line);border-radius:7px;padding:9px 10px}
.seg{display:inline-flex;border:1px solid var(--line);border-radius:7px;overflow:hidden;background:var(--field)}
.seg button{border:0;background:transparent;color:var(--muted);font-family:var(--sans);font-size:13px;padding:7px 14px;cursor:pointer}
.seg button[aria-pressed="true"]{background:var(--ink);color:var(--surface)}
.btn{border:1px solid var(--line);background:var(--field);color:var(--ink);border-radius:7px;padding:7px 12px;font-family:var(--sans);font-size:13px;cursor:pointer;justify-self:start}
.btn:hover{border-color:var(--copper)}

/* result */
.out{background:var(--copper-soft);border:1px solid var(--copper-line);border-radius:9px;padding:16px 18px;display:grid;gap:10px;align-content:start}
.out .k{font-size:12px;color:var(--muted);letter-spacing:.06em}
.out .big{font-family:var(--mono);font-size:clamp(26px,4vw,32px);font-weight:600;color:var(--copper);line-height:1.2;font-variant-numeric:tabular-nums;overflow-wrap:anywhere}
.out dl{margin:0;display:grid;grid-template-columns:auto 1fr;gap:6px 16px;font-size:14px}
.out dt{color:var(--muted)}
.out dd{margin:0;font-family:var(--mono);font-variant-numeric:tabular-nums;text-align:right}
.out .formula{font-family:var(--mono);font-size:12.5px;color:var(--muted);border-top:1px dashed var(--copper-line);padding-top:10px;overflow-wrap:anywhere}
.warn{background:var(--warn-bg);color:var(--warn);border-radius:7px;padding:8px 12px;font-size:13.5px}
.sub{font-size:13px;color:var(--muted);margin:0}
.explain{margin-top:22px;border-top:1px solid var(--line);padding-top:16px;max-width:66ch;color:var(--ink);font-size:14.5px}
.explain h3{margin:0 0 6px;font-size:15px}
.explain p{margin:0 0 8px}
.explain code{font-family:var(--mono);font-size:13px}

/* resistor */
.resistor-fig{width:100%;max-width:420px;height:auto;display:block}
.bands{display:grid;gap:10px;grid-template-columns:repeat(auto-fit,minmax(120px,1fr))}

footer.foot{border-top:1px solid var(--line);color:var(--muted);font-size:13px}
footer.foot .wrap{padding-block:20px 32px;display:flex;flex-wrap:wrap;gap:8px 24px;justify-content:space-between}
@media (prefers-reduced-motion:no-preference){.out .big{transition:color .2s}}

/* multi-page additions */
html{color-scheme:light}
body{margin:0}
img{max-width:100%}
[hidden]{display:none!important}
.brand .name{display:inline-block;margin:0;font-size:clamp(26px,4vw,34px);font-weight:700;letter-spacing:-.01em;color:var(--mask-ink);text-decoration:none}
.brand .name:hover{text-decoration:underline;text-underline-offset:4px}
.board .right{display:grid;gap:10px;justify-items:end}
@media (max-width:640px){.board .right{justify-items:start}}
.lang{font-size:13px;color:var(--mask-ink);border:1px solid rgba(255,255,255,.28);border-radius:999px;padding:3px 12px;text-decoration:none}
.lang:hover{border-color:var(--mask-ink)}
.calc h1{margin:0;font-size:24px;font-weight:700;letter-spacing:-.01em;text-wrap:balance}
.faq{margin-top:22px;border-top:1px solid var(--line);padding-top:16px;max-width:66ch}
.faq h2{font-size:15px;margin:0 0 4px}
.faq details{border-bottom:1px solid var(--line);padding-block:10px}
.faq summary{cursor:pointer;font-weight:600;font-size:14.5px}
.faq details p{margin:6px 0 0;font-size:14.5px;color:var(--ink)}
.intro{max-width:66ch;padding-block:18px 6px}
.intro h2{font-size:18px;margin:0 0 6px}
.intro p{margin:0 0 8px;color:var(--muted)}
.hub{list-style:none;margin:0;padding:0;display:grid;gap:12px;grid-template-columns:repeat(auto-fill,minmax(min(100%,240px),1fr))}
.hub a{display:grid;gap:4px;height:100%;background:var(--surface);border:1px solid var(--line);border-radius:10px;padding:16px 18px;color:var(--ink);text-decoration:none}
.hub a:hover{border-color:var(--copper)}
.hub .ref{font-family:var(--mono);font-size:12px;color:var(--copper);letter-spacing:.06em}
.hub strong{font-size:16px}
.hub .d{font-size:13.5px;color:var(--muted)}
.pagebody{padding-block:14px 48px}
.doc{background:var(--surface);border:1px solid var(--line);border-radius:10px;padding:22px clamp(16px,3vw,28px) 26px;max-width:780px}
.doc h1{font-size:24px;margin:0 0 6px}
.doc h2{font-size:16px;margin:22px 0 6px}
.doc p,.doc li{max-width:66ch}
.doc .sub{margin-bottom:10px}
nav.list li.cat{font-family:var(--mono);font-size:11px;letter-spacing:.1em;text-transform:uppercase;color:var(--muted);padding:14px 12px 4px}
nav.list li.cat:first-child{padding-top:0}
@media (max-width:879px){nav.list li.cat{display:none}}
.cat-h{font-family:var(--mono);font-size:12px;font-weight:500;letter-spacing:.1em;text-transform:uppercase;color:var(--muted);margin:28px 0 10px}
.chip-fig{width:100%;max-width:300px;height:auto;display:block}
label.chk{display:flex;align-items:center;gap:8px;font-size:14px;color:var(--ink);cursor:pointer}
label.chk input{width:16px;height:16px;accent-color:var(--copper)}
/* charts */
:root{--chart:#A35C22;--chart2:#3570B0}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]){--chart:#C4834A;--chart2:#5B8FD0}}
:root[data-theme="dark"]{--chart:#C4834A;--chart2:#5B8FD0}
.plots{margin-top:22px;border-top:1px solid var(--line);padding-top:16px}
.plots-head{display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;gap:10px;margin-bottom:12px}
.plots-head h3{margin:0;font-size:15px}
.plot-grid{display:grid;gap:18px 16px;grid-template-columns:repeat(auto-fit,minmax(min(100%,240px),1fr))}
figure.plot{margin:0;min-width:0}
figure.plot figcaption{font-size:13px;color:var(--muted);margin-bottom:4px}
.ch{position:relative;min-height:176px}
.ch svg{display:block;width:100%;height:auto;touch-action:pan-y}
.ch-grid{stroke:var(--line);stroke-width:1}
.ch-axis{stroke:var(--muted);stroke-width:1;opacity:.6}
.ch-tx{fill:var(--muted);font-family:var(--mono);font-size:10.5px}
.ch-line{fill:none;stroke:var(--chart);stroke-width:2;stroke-linejoin:round;stroke-linecap:round}
.ch-mark{stroke:var(--muted);stroke-width:1;stroke-dasharray:3 3}
.ch-dot{fill:var(--chart);stroke:var(--surface);stroke-width:2}
.ch-mtx{fill:var(--ink);font-family:var(--mono);font-size:10.5px}
.ch-hair{stroke:var(--ink);stroke-width:1;opacity:.35}
.ch-tip{position:absolute;top:0;pointer-events:none;background:var(--ink);color:var(--surface);font-family:var(--mono);font-size:12px;padding:3px 8px;border-radius:6px;white-space:nowrap;transform:translateX(-50%)}
.ch-note{margin:4px 0 0;font-size:12.5px;color:var(--muted)}
.ch-line.s2{stroke:var(--chart2)}
.ch-dot.s2{fill:var(--chart2)}
.ch-legend{display:flex;gap:14px;font-size:12px;color:var(--muted);margin-bottom:2px}
.ch-legend i{display:inline-block;width:14px;height:2px;border-radius:1px;background:var(--chart);vertical-align:middle;margin-right:5px}
.ch-legend i.s2{background:var(--chart2)}
footer.foot a{color:var(--muted)}
footer.foot nav{display:flex;gap:16px;flex-wrap:wrap}