/* FET Lab — bench look: breadboard-white paper in light, scope-screen night in dark.
   Colours follow oscilloscope channel conventions in pastel: load current = CH3 magenta (token --copper,
   kept for API compatibility), control signal = CH2 cyan (--signal), UI accent = periwinkle, plus
   resistor-band pastels for decoration only.
   Layout: slim top bar, chapter sidebar with breadboard-hole texture (drawer on phones),
   one reading column, flat instrument-style lab panels. */
:root {
  --bg: #F5F6FA;
  --surface: #FFFFFF;
  --panel: #EEF0F7;
  --panel-2: #E2E6F2;
  --scope: #F8F9FD;
  --ink: #1E2235;
  --ink-2: #3D4360;
  --muted: #6B7290;
  --line: #D8DCEA;
  --hole: #D3D8E8;

  --accent: #5F5BD8;          /* periwinkle: UI selection, buttons */
  --accent-soft: #E7E6FB;
  --accent-ink: #FFFFFF;
  --mask: var(--accent);      /* legacy aliases */
  --mask-ink: var(--accent-ink);

  --copper: #C2408A;          /* CH3 magenta — load / power current */
  --copper-soft: rgba(194, 64, 138, .12);
  --signal: #13849B;          /* CH2 cyan — gate / base / control */
  --signal-soft: rgba(19, 132, 155, .12);
  --ch1: #B58A00;             /* CH1 yellow — spare trace colour */
  --ok: #24895C;
  --warn: #AE6A00;
  --bad: #CF3F52;
  --ok-soft: rgba(36, 137, 92, .12);
  --warn-soft: rgba(174, 106, 0, .13);
  --bad-soft: rgba(207, 63, 82, .12);

  /* resistor colour bands (pastel), decoration */
  --band-1: #F4A6B8; --band-2: #F9CF8B; --band-3: #A9DFC0; --band-4: #A9C8F5; --band-5: #CDB8F2;

  --grid: rgba(30, 34, 53, .075);

  --f-display: "Bai Jamjuree", "Segoe UI", system-ui, sans-serif;
  --f-body: "Atkinson Hyperlegible", "Segoe UI", system-ui, -apple-system, sans-serif;
  --f-mono: "JetBrains Mono", ui-monospace, "Cascadia Mono", Consolas, monospace;

  --fs-0: .8125rem; --fs-1: .97rem; --fs-2: 1.08rem; --fs-3: 1.28rem; --fs-4: 1.62rem; --fs-5: 2.2rem;
  --r: 6px;
  --top: 54px;
  --side: 268px;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #12141D; --surface: #191C28; --panel: #1F2332; --panel-2: #282D40; --scope: #0F1119;
    --ink: #E9EBF5; --ink-2: #C3C7DA; --muted: #959BB6; --line: #2E3347; --hole: #2A2F42;
    --accent: #A9A6FF; --accent-soft: rgba(169, 166, 255, .14); --accent-ink: #14152A;
    --copper: #FF9ACB; --copper-soft: rgba(255, 154, 203, .14);
    --signal: #7ADDEB; --signal-soft: rgba(122, 221, 235, .13);
    --ch1: #F6D776;
    --ok: #8BE0B4; --warn: #FFD37E; --bad: #FF8E9B;
    --ok-soft: rgba(139, 224, 180, .13); --warn-soft: rgba(255, 211, 126, .13); --bad-soft: rgba(255, 142, 155, .14);
    --band-1: #8E4F63; --band-2: #8D6C38; --band-3: #3F7A5B; --band-4: #3F5F92; --band-5: #66558F;
    --grid: rgba(233, 235, 245, .07);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #12141D; --surface: #191C28; --panel: #1F2332; --panel-2: #282D40; --scope: #0F1119;
  --ink: #E9EBF5; --ink-2: #C3C7DA; --muted: #959BB6; --line: #2E3347; --hole: #2A2F42;
  --accent: #A9A6FF; --accent-soft: rgba(169, 166, 255, .14); --accent-ink: #14152A;
  --copper: #FF9ACB; --copper-soft: rgba(255, 154, 203, .14);
  --signal: #7ADDEB; --signal-soft: rgba(122, 221, 235, .13);
  --ch1: #F6D776;
  --ok: #8BE0B4; --warn: #FFD37E; --bad: #FF8E9B;
  --ok-soft: rgba(139, 224, 180, .13); --warn-soft: rgba(255, 211, 126, .13); --bad-soft: rgba(255, 142, 155, .14);
  --band-1: #8E4F63; --band-2: #8D6C38; --band-3: #3F7A5B; --band-4: #3F5F92; --band-5: #66558F;
  --grid: rgba(233, 235, 245, .07);
  color-scheme: dark;
}

*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-padding-top: calc(var(--top) + 16px); }
body {
  margin: 0; background: var(--bg); color: var(--ink);
  font: 400 var(--fs-1)/1.62 var(--f-body);
}
[hidden] { display: none !important; }
img, svg { max-width: 100%; }
a { color: var(--accent); text-underline-offset: 2px; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 3px; }
code, kbd, .mono { font-family: var(--f-mono); font-size: .88em; }
code { background: var(--panel); padding: .08em .35em; border-radius: 3px; }
b, strong { font-weight: 700; }

/* ---------- top bar ---------- */
.topbar {
  position: sticky; top: env(safe-area-inset-top, 0px); z-index: 30; height: var(--top);
  display: flex; align-items: center; gap: 12px;
  padding-left: max(16px, env(safe-area-inset-left, 0px)); padding-right: max(16px, env(safe-area-inset-right, 0px));
  background: var(--surface); color: var(--ink); border-bottom: 1px solid var(--line);
}
/* resistor colour-band stripe under the bar */
.topbar::after {
  content: ""; position: absolute; left: 0; right: 0; bottom: -4px; height: 3px;
  background: linear-gradient(90deg, var(--band-1) 0 20%, var(--band-2) 20% 40%, var(--band-3) 40% 60%, var(--band-4) 60% 80%, var(--band-5) 80%);
  opacity: .9;
}
.brand { display: flex; align-items: center; gap: 10px; color: inherit; text-decoration: none; min-width: 0; }
.brand strong { font: 700 1.15rem/1 var(--f-display); letter-spacing: .01em; display: block; }
.brand small { display: block; font-size: .74rem; color: var(--muted); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; margin-top: 2px; }
.brand-mark { width: 34px; height: 18px; flex: none; }
.brand-mark .lead { stroke: var(--muted); stroke-width: 1.6; }
.brand-mark .body { fill: var(--panel-2); stroke: var(--ink-2); stroke-width: 1.2; }
.top-actions { margin-left: auto; display: flex; gap: 8px; align-items: center; }
.icon-btn { width: 36px; height: 36px; border-radius: var(--r); border: 1px solid var(--line); background: var(--surface); color: var(--ink-2); display: grid; place-items: center; cursor: pointer; }
.icon-btn svg { width: 19px; height: 19px; fill: none; stroke: currentColor; stroke-width: 1.8; stroke-linecap: round; }
.icon-btn:hover { background: var(--panel); color: var(--ink); }
.lang { display: flex; border: 1px solid var(--line); border-radius: var(--r); overflow: hidden; }
.lang button { background: var(--surface); color: var(--muted); border: 0; padding: 7px 10px; font: 600 .78rem var(--f-mono); cursor: pointer; }
.lang button[aria-pressed="true"] { background: var(--accent-soft); color: var(--accent); }
.menu-btn { display: none; }

/* ---------- layout ---------- */
.layout { display: grid; grid-template-columns: var(--side) minmax(0, 1fr); min-height: calc(100vh - var(--top)); }
.sidebar {
  position: sticky; top: calc(var(--top) + env(safe-area-inset-top, 0px)); align-self: start;
  height: calc(100vh - var(--top) - env(safe-area-inset-top, 0px)); overflow-y: auto;
  border-right: 1px solid var(--line);
  background-color: var(--panel);
  /* breadboard holes */
  background-image: radial-gradient(circle, var(--hole) 1.3px, transparent 1.6px);
  background-size: 12px 12px; background-position: 6px 6px;
  padding-block: 12px 40px; padding-left: max(12px, env(safe-area-inset-left, 0px)); padding-right: 12px;
}
.nav-group { font: 600 .74rem/1 var(--f-display); letter-spacing: .04em; color: var(--muted); padding: 18px 10px 7px; display: flex; align-items: center; gap: 8px; }
.nav-group::before { content: ""; width: 10px; height: 4px; border-radius: 2px; background: var(--band-4); }
.nav > .nav-group:nth-of-type(6n+1)::before { background: var(--band-1); }
.nav > .nav-group:nth-of-type(6n+2)::before { background: var(--band-2); }
.nav > .nav-group:nth-of-type(6n+3)::before { background: var(--band-3); }
.nav > .nav-group:nth-of-type(6n+4)::before { background: var(--band-4); }
.nav > .nav-group:nth-of-type(6n+5)::before { background: var(--band-5); }
.nav-list { list-style: none; margin: 0; padding: 0; display: grid; gap: 1px; }
.nav-list a { display: flex; gap: 10px; align-items: baseline; padding: 6px 10px; border-radius: var(--r); color: var(--ink-2); text-decoration: none; font-size: .9rem; line-height: 1.3; }
.nav-list a:hover { background: var(--surface); color: var(--ink); }
.nav-list a.active { background: var(--accent-soft); color: var(--accent); font-weight: 700; }
.nav-list a.active .nav-num { color: var(--accent); }
.nav-num { font: 500 .72rem var(--f-mono); color: var(--muted); min-width: 1.9em; }
.scrim { display: none; }

.main { min-width: 0; padding-left: max(16px, env(safe-area-inset-left, 0px)); padding-right: max(16px, env(safe-area-inset-right, 0px)); padding-block: 30px 60px; }
.page { max-width: 980px; margin: 0 auto; }
.page-head { padding-bottom: 20px; margin-bottom: 26px; border-bottom: 1px dashed var(--line); }
.eyebrow { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; margin-bottom: 8px; font: 500 .8rem var(--f-mono); color: var(--muted); }
.chip { color: var(--accent); }
.chip::after { content: " /"; color: var(--muted); }
.pnum { color: var(--muted); }
h1, h2, h3, h4 { font-family: var(--f-display); text-wrap: balance; line-height: 1.18; margin: 0; }
h1 { font-size: var(--fs-5); font-weight: 700; letter-spacing: -.01em; }
h2 { font-size: var(--fs-4); font-weight: 600; margin-top: 46px; margin-bottom: 12px; }
h3 { font-size: var(--fs-3); font-weight: 600; margin-top: 28px; margin-bottom: 8px; }
h4 { font-size: var(--fs-2); font-weight: 600; margin-top: 18px; margin-bottom: 6px; }
.page-body > h2:first-child { margin-top: 0; }
.lead { font-size: var(--fs-2); color: var(--ink-2); max-width: 68ch; margin: 12px 0 0; }
.page-body p, .page-body li { max-width: 72ch; }
.page-body ul, .page-body ol { padding-left: 1.3em; }
.page-body li + li { margin-top: 4px; }
.muted { color: var(--muted); }
.small { font-size: var(--fs-0); }
.cu { color: var(--copper); font-weight: 700; }
.sig { color: var(--signal); font-weight: 700; }

/* ---------- lab panels: flat instrument faces ---------- */
.lab { margin: 22px 0 28px; background: var(--surface); border: 1px solid var(--line); border-radius: var(--r); overflow: hidden; }
.lab-head { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; padding: 10px 14px; border-bottom: 1px solid var(--line); }
.lab-head .tag {
  font: 600 .7rem/1 var(--f-mono); color: var(--ink-2); display: inline-flex; align-items: center; gap: 6px;
  padding: 4px 8px 4px 6px; border-radius: 99px; background: var(--panel);
}
/* status LED on each panel */
.lab-head .tag::before { content: ""; width: 7px; height: 7px; border-radius: 50%; background: var(--ok); box-shadow: 0 0 0 2px var(--ok-soft); }
.lab-head h3, .lab-head h4 { margin: 0; font-size: 1.05rem; }
.lab-body { display: grid; grid-template-columns: minmax(0, 1.55fr) minmax(220px, 1fr); }
.lab-body.stack { grid-template-columns: minmax(0, 1fr); }
.lab-fig { min-width: 0; padding: 14px; display: grid; gap: 10px; align-content: start; }
.lab-ctl { min-width: 0; padding: 14px 16px; border-left: 1px solid var(--line); display: grid; gap: 14px; align-content: start; background: var(--panel); }
.lab-body.stack .lab-ctl { border-left: 0; border-top: 1px solid var(--line); grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); }
.lab-foot { padding: 10px 14px; border-top: 1px dashed var(--line); font-size: var(--fs-0); color: var(--muted); }
.fig-cap { font-size: var(--fs-0); color: var(--muted); }
.two { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; }

/* controls */
.ctl { display: grid; gap: 6px; }
.ctl-label { display: block; font-size: .86rem; color: var(--ink-2); }
.ctl label { display: flex; justify-content: space-between; gap: 8px; font-size: .86rem; color: var(--ink-2); }
.ctl output { font: 500 .84rem var(--f-mono); color: var(--ink); font-variant-numeric: tabular-nums; white-space: nowrap; }
input[type=range] { -webkit-appearance: none; appearance: none; width: 100%; height: 22px; background: transparent; margin: 0; cursor: pointer; --p: 50%; }
input[type=range]::-webkit-slider-runnable-track { height: 4px; border-radius: 99px; background: linear-gradient(90deg, var(--accent) var(--p), var(--panel-2) var(--p)); }
input[type=range]::-moz-range-track { height: 4px; border-radius: 99px; background: var(--panel-2); }
input[type=range]::-moz-range-progress { height: 4px; border-radius: 99px; background: var(--accent); }
input[type=range]::-webkit-slider-thumb { -webkit-appearance: none; width: 16px; height: 16px; border-radius: 4px; background: var(--surface); border: 2px solid var(--accent); margin-top: -6px; }
input[type=range]::-moz-range-thumb { width: 12px; height: 12px; border-radius: 4px; background: var(--surface); border: 2px solid var(--accent); }
.seg { display: flex; flex-wrap: wrap; gap: 4px; }
.seg button { flex: 1 1 auto; border: 1px solid var(--line); border-radius: var(--r); background: var(--surface); color: var(--ink-2); padding: 6px 10px; font: 500 .82rem var(--f-body); cursor: pointer; }
.seg button:hover { border-color: var(--accent); }
.seg button[aria-pressed="true"] { background: var(--accent-soft); border-color: var(--accent); color: var(--accent); font-weight: 700; }
.ctl-toggle { display: flex; align-items: center; gap: 10px; font-size: .88rem; }
.switch { width: 40px; height: 22px; border-radius: 99px; border: 1px solid var(--line); background: var(--panel-2); position: relative; cursor: pointer; flex: none; padding: 0; }
.switch .knob { position: absolute; top: 2px; left: 2px; width: 16px; height: 16px; border-radius: 50%; background: var(--surface); border: 1px solid var(--line); transition: left .16s; }
.switch[aria-checked="true"] { background: var(--accent); border-color: var(--accent); }
.switch[aria-checked="true"] .knob { left: 20px; border-color: transparent; }
.btn { border: 1px solid var(--line); background: var(--surface); color: var(--ink); padding: 7px 14px; border-radius: var(--r); font: 500 .88rem var(--f-body); cursor: pointer; }
.btn:hover { border-color: var(--accent); color: var(--accent); }
.btn.primary { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
.btn.primary:hover { filter: brightness(1.06); color: var(--accent-ink); }
select, input[type=number], input[type=text] {
  font: 500 .88rem var(--f-body); color: var(--ink); background: var(--surface);
  border: 1px solid var(--line); border-radius: var(--r); padding: 6px 8px; width: 100%;
}

/* readouts look like an LCD/DMM strip */
.readouts { margin: 0; display: grid; gap: 0; border: 1px solid var(--line); border-radius: var(--r); overflow: hidden; background: var(--surface); }
.ro { display: flex; justify-content: space-between; gap: 10px; padding: 6px 10px; font-size: .84rem; }
.ro + .ro { border-top: 1px dashed var(--line); }
.ro dt { color: var(--muted); }
.ro dd { margin: 0; font: 500 .84rem var(--f-mono); font-variant-numeric: tabular-nums; text-align: right; }
.ro[data-state="ok"] dd { color: var(--ok); }
.ro[data-state="warn"] dd { color: var(--warn); }
.ro[data-state="bad"] dd { color: var(--bad); }
.ro[data-state="bad"] { background: var(--bad-soft); }

.status { padding: 8px 12px; border-radius: var(--r); font-size: .86rem; font-weight: 700; }
.status.ok { background: var(--ok-soft); color: var(--ok); }
.status.warn { background: var(--warn-soft); color: var(--warn); }
.status.bad { background: var(--bad-soft); color: var(--bad); }

/* ---------- plots: scope screen ---------- */
.plot { width: 100%; height: auto; display: block; font-family: var(--f-mono); }
.plot .bgbox { fill: var(--scope); stroke: var(--line); stroke-width: 1; }
.plot .gl { stroke: var(--grid); stroke-width: 1; stroke-dasharray: 2 3; }
.plot .axis { stroke: var(--muted); stroke-width: 1.1; fill: none; }
.plot .tick { fill: var(--muted); font-size: 10.5px; }
.plot .alabel { fill: var(--ink-2); font-size: 11.5px; font-family: var(--f-body); }
.plot .pl { fill: none; stroke: var(--ink-2); stroke-width: 2; stroke-linejoin: round; }
.plot .pl.faint { stroke: var(--muted); stroke-width: 1.2; opacity: .45; }
.plot .pl.cu { stroke: var(--copper); stroke-width: 2.4; }
.plot .pl.sig { stroke: var(--signal); stroke-width: 2.2; }
.plot .pl.ok { stroke: var(--ok); }
.plot .pl.bad { stroke: var(--bad); }
.plot .pl.warn { stroke: var(--warn); }
.plot .pl.ch1 { stroke: var(--ch1); }
.plot .pl.acc { stroke: var(--accent); }
.plot .pl.dash { stroke-dasharray: 5 4; }
.plot .pl.thin { stroke-width: 1.3; }
.plot .pa { fill: var(--copper-soft); stroke: none; }
.plot .pa.sig { fill: var(--signal-soft); }
.plot .pa.bad { fill: var(--bad-soft); }
.plot .pa.ok { fill: var(--ok-soft); }
.plot .pa.warn { fill: var(--warn-soft); }
.plot .pr { fill: var(--panel); stroke: none; }
.plot .pr.sig { fill: var(--signal-soft); }
.plot .pr.cu { fill: var(--copper-soft); }
.plot .pr.bad { fill: var(--bad-soft); }
.plot .pr.ok { fill: var(--ok-soft); }
.plot .pr.warn { fill: var(--warn-soft); }
.plot .pd { fill: var(--copper); stroke: var(--surface); stroke-width: 2; }
.plot .pd.sig { fill: var(--signal); }
.plot .pd.bad { fill: var(--bad); }
.plot .pd.ok { fill: var(--ok); }
.plot .pd.acc { fill: var(--accent); }
.plot .pv { stroke: var(--muted); stroke-width: 1; stroke-dasharray: 4 4; }
.plot .pv.cu { stroke: var(--copper); }
.plot .pv.sig { stroke: var(--signal); }
.plot .pv.bad { stroke: var(--bad); }
.plot .pv.ok { stroke: var(--ok); }
.plot .pv.acc { stroke: var(--accent); }
.plot .pv.solid { stroke-dasharray: none; stroke-width: 1.5; }
.plot .pt { fill: var(--ink-2); font-size: 11px; font-family: var(--f-body); }
.plot .pt.cu { fill: var(--copper); font-weight: 700; }
.plot .pt.sig { fill: var(--signal); font-weight: 700; }
.plot .pt.bad { fill: var(--bad); font-weight: 700; }
.plot .pt.ok { fill: var(--ok); font-weight: 700; }
.plot .pt.warn { fill: var(--warn); font-weight: 700; }
.plot .pt.muted { fill: var(--muted); }
.plot .pt.big { font-size: 13px; font-weight: 700; }

/* ---------- oscilloscope (Viz.Scope): the instrument keeps its own dark glass in both themes ---------- */
:root {
  --scr-bg: #0E1219; --scr-glass: #121823; --scr-grid: rgba(196, 210, 255, .13); --scr-axis: rgba(196, 210, 255, .32);
  --scr-text: #C9D1EA; --scr-dim: #8590AE;
  --scr-ch1: #F4D67A; --scr-ch2: #7FDDEB; --scr-ch3: #FF9FCC; --scr-ch4: #ABA8FF; --scr-ok: #8DE3B6; --scr-bad: #FF8F9C;
}
.scope { width: 100%; height: auto; display: block; font-family: var(--f-mono); }
.scope .sc-bezel { fill: var(--scr-bg); stroke: var(--line); }
.scope .sc-screen { fill: var(--scr-glass); }
.scope .sc-div { stroke: var(--scr-grid); stroke-width: 1; stroke-dasharray: 1 4; }
.scope .sc-axis { stroke: var(--scr-axis); stroke-width: 1; }
.scope .sc-tick { stroke: var(--scr-axis); stroke-width: 1; }
.scope .sc-frame { fill: none; stroke: var(--scr-axis); stroke-width: 1; }
.scope .c-ch1 { color: var(--scr-ch1); } .scope .c-ch2 { color: var(--scr-ch2); } .scope .c-ch3 { color: var(--scr-ch3); }
.scope .c-ch4 { color: var(--scr-ch4); } .scope .c-ok { color: var(--scr-ok); } .scope .c-bad { color: var(--scr-bad); }
.scope .sc-trace { fill: none; stroke: currentColor; stroke-width: 2; stroke-linejoin: round; filter: drop-shadow(0 0 2.5px currentColor); }
.scope .sc-tag { fill: currentColor; }
.scope .sc-tagt { fill: var(--scr-bg); font-size: 10.5px; font-weight: 700; }
.scope .sc-name { fill: currentColor; font-size: 11px; font-weight: 500; }
.scope .sc-status { fill: var(--scr-dim); font-size: 10.5px; letter-spacing: .06em; }
.scope .sc-scale { fill: var(--scr-text); font-size: 10.5px; }
.scope .sc-time { fill: var(--scr-text); font-weight: 600; }
.scope .sc-meas { fill: currentColor; font-size: 10.5px; }
.scope .sc-dot { fill: currentColor; }
.scope .sc-gnd { fill: currentColor; }
.scope .sc-gndt { fill: var(--scr-bg); font-size: 9.5px; font-weight: 700; }
.scope .sc-trig { fill: var(--scr-ch1); }
.scope .sc-trigt { fill: var(--scr-ch1); font-size: 10px; font-weight: 700; }
.scope .sc-cursor { stroke: var(--scr-text); stroke-width: 1; stroke-dasharray: 3 3; opacity: .55; }

/* ---------- schematics ---------- */
.sch-wrap { overflow-x: auto; }
.schem { width: 100%; height: auto; display: block; font-family: var(--f-mono); }
.schem .wire { fill: none; stroke: var(--ink-2); stroke-width: 1.7; stroke-linejoin: round; stroke-linecap: round; }
.schem .wire.hot { stroke: var(--copper); }
.schem .wire.sigw { stroke: var(--signal); }
.schem .sch path, .schem .sch rect, .schem .sch circle { fill: none; stroke: var(--ink); stroke-width: 1.7; stroke-linejoin: round; stroke-linecap: round; }
.schem .sch .fillink { fill: var(--ink); stroke: none; }
.schem .sch .thin { stroke-width: 1.2; }
.schem .sch .tbody, .schem .sch .load-body, .schem .sch .ic-body { fill: var(--surface); }
.schem .sch.ic .ic-body { fill: var(--panel); }
.schem .sch .bd path { stroke-width: 1.3; }
.schem .sch .bd .fillink { fill: var(--ink); }
.schem .led .led-glow { fill: var(--copper); stroke: none; opacity: 0; transition: opacity .15s; filter: blur(5px); }
.schem .jdot { fill: var(--ink-2); }
.schem .sch-t { fill: var(--ink-2); font-size: 11px; }
.schem .sch-t.rail { fill: var(--ink); font-weight: 700; }
.schem .sch-t.ic-t { fill: var(--ink); font-weight: 700; font-family: var(--f-display); font-size: 13px; }
.schem .sch-t.ic-s { fill: var(--muted); font-size: 10px; }
.schem .sch-t.pm { fill: var(--muted); }
.schem .sch-t.cu, .schem .lbl.cu { fill: var(--copper); font-weight: 700; }
.schem .sch-t.sig, .schem .lbl.sig { fill: var(--signal); font-weight: 700; }
.schem .sch-t.bad { fill: var(--bad); font-weight: 700; }
.schem .sch-t.ok { fill: var(--ok); font-weight: 700; }
.schem .sch-t.warn { fill: var(--warn); font-weight: 700; }
.schem .sch-t.muted { fill: var(--muted); }
.schem .sch-t.big { font-size: 13px; font-weight: 700; }
.schem .flow-track { fill: none; stroke: none; }
.schem .flow circle, .plot .flow circle { fill: var(--copper); }
.schem .flow.e circle { fill: var(--signal); }
.schem .flow.bad circle { fill: var(--bad); }
.schem .flow { transition: opacity .2s; }
/* semiconductor cross-sections: n = cyan tint, p = magenta tint */
.schem .layer { stroke: var(--line); stroke-width: 1; }
.schem .layer.n { fill: color-mix(in srgb, var(--signal) 24%, var(--surface)); }
.schem .layer.n2 { fill: color-mix(in srgb, var(--signal) 12%, var(--surface)); }
.schem .layer.p { fill: color-mix(in srgb, var(--copper) 18%, var(--surface)); }
.schem .layer.ox { fill: color-mix(in srgb, var(--ch1) 30%, var(--surface)); }
.schem .layer.metal { fill: var(--muted); }
.schem .layer.chan { fill: var(--signal); opacity: .55; }
.schem .hl { fill: none; stroke: var(--copper); stroke-width: 6; opacity: .18; stroke-linecap: round; stroke-linejoin: round; }

/* ---------- content blocks ---------- */
.eq {
  font: 500 .98rem/1.55 var(--f-mono); background: var(--scope); border: 1px solid var(--line);
  border-radius: var(--r); padding: 12px 16px; margin: 14px 0; overflow-x: auto; color: var(--ink);
}
.eq .note { display: block; font: 400 .84rem/1.5 var(--f-body); color: var(--muted); margin-top: 6px; }
.eq b { color: var(--copper); font-weight: 600; }
.call { border-radius: var(--r); padding: 11px 14px 11px 42px; margin: 16px 0; position: relative; font-size: .94rem; background: var(--panel); }
.call::before { position: absolute; left: 13px; top: 12px; width: 18px; height: 18px; border-radius: 4px; display: grid; place-items: center; font: 700 .76rem var(--f-mono); }
.call.tip { background: var(--ok-soft); }
.call.tip::before { content: "✓"; background: var(--ok); color: var(--surface); }
.call.warn { background: var(--warn-soft); }
.call.warn::before { content: "!"; background: var(--warn); color: var(--surface); }
.call.bad { background: var(--bad-soft); }
.call.bad::before { content: "×"; background: var(--bad); color: var(--surface); }
.call.info { background: var(--signal-soft); }
.call.info::before { content: "i"; background: var(--signal); color: var(--surface); }
.call strong:first-child { display: block; margin-bottom: 2px; }
.call p { margin: 4px 0; }

.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 12px; margin: 16px 0; }
.card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--r); padding: 14px 16px; min-width: 0; }
.card h4 { margin-top: 0; }
.card p { margin: 6px 0 0; font-size: .9rem; color: var(--ink-2); }
a.card { text-decoration: none; color: inherit; display: block; transition: border-color .15s, background .15s; }
a.card:hover { border-color: var(--accent); background: var(--accent-soft); }
.card .k { font: 500 .72rem var(--f-mono); color: var(--muted); }

.table-wrap { overflow-x: auto; margin: 16px 0; border: 1px solid var(--line); border-radius: var(--r); background: var(--surface); }
table { border-collapse: collapse; width: 100%; font-size: .88rem; }
th, td { text-align: left; padding: 8px 12px; border-bottom: 1px solid var(--line); vertical-align: top; }
th { font: 600 .8rem var(--f-display); color: var(--ink-2); background: var(--panel); white-space: nowrap; }
tbody tr:hover td { background: var(--scope); }
tr:last-child td { border-bottom: 0; }
td.num, th.num { text-align: right; font-family: var(--f-mono); font-variant-numeric: tabular-nums; white-space: nowrap; }

.steps { counter-reset: s; list-style: none; padding-left: 0 !important; }
.steps > li { counter-increment: s; position: relative; padding-left: 38px; margin-top: 10px; }
.steps > li::before { content: counter(s); position: absolute; left: 0; top: 0; width: 25px; height: 25px; border-radius: 4px; background: var(--accent-soft); color: var(--accent); font: 700 .8rem/25px var(--f-mono); text-align: center; }

.tabs { margin: 18px 0; }
.tab-btns { display: flex; gap: 4px; flex-wrap: wrap; margin-bottom: 14px; }
.tab-btns button { border: 1px solid var(--line); border-radius: var(--r); background: var(--surface); padding: 7px 13px; font: 500 .88rem var(--f-body); color: var(--ink-2); cursor: pointer; }
.tab-btns button:hover { border-color: var(--accent); }
.tab-btns button[aria-selected="true"] { color: var(--accent); background: var(--accent-soft); border-color: var(--accent); font-weight: 700; }

details.fold { border: 1px solid var(--line); border-radius: var(--r); background: var(--surface); margin: 12px 0; }
details.fold > summary { cursor: pointer; padding: 10px 14px; font-weight: 700; list-style: none; }
details.fold > summary::-webkit-details-marker { display: none; }
details.fold > summary::before { content: "+"; font-family: var(--f-mono); color: var(--accent); margin-right: 8px; }
details.fold[open] > summary::before { content: "−"; }
details.fold > div { padding: 0 14px 12px; }

.kbd-row { display: flex; gap: 8px; flex-wrap: wrap; }
.pill { display: inline-block; font: 500 .74rem var(--f-mono); padding: 2px 8px; border-radius: 99px; background: var(--panel); color: var(--ink-2); }
.pill.ok { background: var(--ok-soft); color: var(--ok); }
.pill.bad { background: var(--bad-soft); color: var(--bad); }
.pill.warn { background: var(--warn-soft); color: var(--warn); }
.pill.cu { background: var(--copper-soft); color: var(--copper); }
.pill.sig { background: var(--signal-soft); color: var(--signal); }

/* pager */
.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 56px; padding-top: 20px; border-top: 1px dashed var(--line); }
.pager-btn { display: grid; gap: 2px; padding: 12px 16px; border: 1px solid var(--line); border-radius: var(--r); text-decoration: none; color: var(--ink); background: var(--surface); }
.pager-btn small { color: var(--muted); font: 500 .74rem var(--f-mono); }
.pager-btn span { font-family: var(--f-display); font-weight: 600; font-size: 1.04rem; }
.pager-btn.next { text-align: right; }
.pager-btn:hover { border-color: var(--accent); background: var(--accent-soft); }

/* ---------- embed mode (?embed): no top bar or menu, content only ---------- */
.embed .topbar, .embed .sidebar, .embed .scrim { display: none !important; }
.embed .layout { grid-template-columns: minmax(0, 1fr); min-height: 0; }
.embed .main { padding-block: 16px 24px; }
.embed .sidebar ~ .main { padding-top: 16px; }
.embed .pager { display: none; }
.embed.embed-nav .pager { display: grid; }
.embed body { padding-top: 0; }
html.embed-auto, html.embed-auto body { overflow: hidden; }

/* ---------- responsive ---------- */
@media (max-width: 900px) {
  .lab-body { grid-template-columns: minmax(0, 1fr); }
  .lab-ctl { border-left: 0; border-top: 1px solid var(--line); }
}
@media (max-width: 820px) {
  :root { --fs-5: 1.8rem; --fs-4: 1.42rem; }
  .menu-btn { display: grid; }
  .layout { grid-template-columns: minmax(0, 1fr); }
  .sidebar {
    position: fixed; z-index: 40; left: 0; top: calc(var(--top) + env(safe-area-inset-top, 0px)); bottom: 0;
    height: auto; width: min(300px, 86vw); transform: translateX(-102%); transition: transform .22s ease;
    padding-bottom: calc(40px + env(safe-area-inset-bottom, 0px));
  }
  body.nav-open .sidebar { transform: none; }
  body.nav-open .scrim { display: block; position: fixed; inset: 0; z-index: 35; background: rgba(10, 12, 20, .35); }
  .two { grid-template-columns: minmax(0, 1fr); }
  .brand small { display: none; }
}
@media (max-width: 480px) {
  .pager { grid-template-columns: minmax(0, 1fr); }
  .pager-btn.next { text-align: left; }
  .lab-fig { padding: 10px; }
}
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { transition: none !important; animation: none !important; }
}

/* =====================================================================
   Calm reading pass: icons, more air, tiles instead of dense lists.
   (appended last so it wins over the base rules above)
   ===================================================================== */
:root { --fs-1: 1.02rem; --fs-2: 1.1rem; }
body { line-height: 1.72; }
.page { max-width: 1000px; }
.page-body p { margin: 0 0 1.05em; }
.page-body p, .page-body li { max-width: 68ch; }
.page-body li + li { margin-top: 8px; }
h2 { margin-top: 64px; margin-bottom: 16px; }
h3 { margin-top: 36px; margin-bottom: 10px; }

/* line icons */
.ic { width: 1em; height: 1em; fill: none; stroke: currentColor; stroke-width: 1.8; stroke-linecap: round; stroke-linejoin: round; flex: none; vertical-align: -0.15em; }
.ic .ic-fill { fill: currentColor; stroke: none; }

/* chapter header: icon tile + text */
.page-head { display: grid; grid-template-columns: auto minmax(0, 1fr); gap: 20px; align-items: start; padding-bottom: 28px; margin-bottom: 36px; }
.head-ic { width: 64px; height: 64px; border-radius: 16px; display: grid; place-items: center; background: var(--accent-soft); color: var(--accent); }
.head-ic .ic { width: 34px; height: 34px; stroke-width: 1.6; }
.lead { max-width: 62ch; color: var(--muted); font-size: 1.08rem; }
@media (max-width: 560px) { .page-head { grid-template-columns: minmax(0, 1fr); } .head-ic { width: 52px; height: 52px; } }

/* sidebar: icon, title, small number on the right */
.nav-list a { align-items: center; gap: 10px; padding: 7px 10px; }
.nav-list .nav-ic { width: 18px; height: 18px; color: var(--muted); }
.nav-list a.active .nav-ic, .nav-list a:hover .nav-ic { color: var(--accent); }
.nav-t { flex: 1 1 auto; min-width: 0; }
.nav-num { min-width: 0; font-size: .66rem; opacity: .7; }

/* callouts with icons */
.call { padding: 14px 16px 14px 50px; line-height: 1.6; }
.call::before { content: none !important; }
.call-ic { position: absolute; left: 15px; top: 14px; display: grid; place-items: center; }
.call-ic .ic { width: 22px; height: 22px; }
.call.tip .call-ic { color: var(--ok); } .call.warn .call-ic { color: var(--warn); }
.call.bad .call-ic { color: var(--bad); } .call.info .call-ic, .call:not(.tip):not(.warn):not(.bad) .call-ic { color: var(--signal); }

/* cards with an icon tile */
.card-ic { display: grid !important; grid-template-columns: auto minmax(0, 1fr); gap: 14px; align-items: start; }
.card-ic .tile { width: 42px; height: 42px; border-radius: 12px; display: grid; place-items: center; background: var(--accent-soft); color: var(--accent); }
.card-ic .tile .ic { width: 22px; height: 22px; }
.card-ic h4 { margin: 2px 0 0; font-size: 1rem; }
.card-ic p { font-size: .86rem; color: var(--muted); }
.cards { gap: 14px; }
.card { padding: 16px 18px; }

/* readouts become measurement tiles: label on top, value large */
.readouts { display: grid; grid-template-columns: repeat(auto-fill, minmax(132px, 1fr)); gap: 8px; border: 0; background: transparent; overflow: visible; }
.readouts .ro { flex-direction: column; justify-content: flex-start; gap: 2px; padding: 9px 12px; border: 1px solid var(--line); border-radius: 10px; background: var(--surface); }
.readouts .ro + .ro { border-top: 1px solid var(--line); }
.readouts .ro dt { font-size: .74rem; line-height: 1.3; }
.readouts .ro dd { text-align: left; font-size: 1.02rem; font-weight: 600; line-height: 1.35; white-space: normal; }
.readouts .ro[data-state="ok"] { background: var(--ok-soft); border-color: transparent; }
.readouts .ro[data-state="warn"] { background: var(--warn-soft); border-color: transparent; }
.readouts .ro[data-state="bad"] { background: var(--bad-soft); border-color: transparent; }

/* labs: more breathing room */
.lab { margin: 32px 0 40px; border-radius: 12px; }
.lab-head { padding: 12px 18px; }
.lab-fig { padding: 18px; gap: 14px; }
.lab-ctl { padding: 18px; gap: 18px; }
.lab-foot { padding: 12px 18px; line-height: 1.6; }
.eq { padding: 14px 18px; margin: 20px 0; }
th, td { padding: 10px 14px; }

/* ---------- result-first content blocks ---------- */
/* "In short" box at the top of a page */
.keys { margin: 0 0 36px; padding: 16px 20px; border-radius: 12px; background: var(--accent-soft); }
.keys-t { display: flex; align-items: center; gap: 8px; font: 700 .95rem var(--f-display); color: var(--accent); margin-bottom: 8px; }
.keys-t .ic { width: 20px; height: 20px; }
.keys ul { list-style: none; margin: 0; padding: 0 !important; display: grid; gap: 6px; }
.keys li { position: relative; padding-left: 22px; max-width: none !important; margin: 0 !important; }
.keys li::before { content: ""; position: absolute; left: 4px; top: .7em; width: 7px; height: 7px; border-radius: 50%; background: var(--accent); }

/* worked example: given → calculation rows → result */
.ex { margin: 20px 0; display: grid; gap: 12px; }
.ex-given { display: flex; flex-wrap: wrap; gap: 6px; }
.ex-given .kv { font: 500 .84rem var(--f-mono); padding: 4px 10px; border-radius: 99px; background: var(--panel); border: 1px solid var(--line); }
.ex-given .kv b { font-family: var(--f-body); font-weight: 700; color: var(--muted); margin-right: 6px; }
ol.calc { list-style: none; margin: 0; padding: 0 !important; counter-reset: c; border: 1px solid var(--line); border-radius: 10px; overflow: hidden; background: var(--surface); }
ol.calc > li {
  counter-increment: c; display: grid; grid-template-columns: 28px minmax(130px, 1fr) minmax(0, 1.6fr) auto; gap: 12px; align-items: baseline;
  padding: 10px 14px; margin: 0 !important; max-width: none !important; border-top: 1px dashed var(--line);
}
ol.calc > li:first-child { border-top: 0; }
ol.calc > li::before { content: counter(c); font: 700 .78rem var(--f-mono); color: var(--accent); }
ol.calc .c-what { color: var(--ink-2); font-size: .92rem; }
ol.calc .c-f { font: 500 .9rem var(--f-mono); color: var(--ink); overflow-wrap: anywhere; }
ol.calc .c-r { font: 700 .95rem var(--f-mono); color: var(--accent); white-space: nowrap; text-align: right; }
ol.calc .c-n { grid-column: 2 / -1; font-size: .84rem; color: var(--muted); margin-top: -4px; }
@media (max-width: 640px) {
  ol.calc > li { grid-template-columns: 22px minmax(0, 1fr) auto; }
  ol.calc .c-f { grid-column: 2 / -1; grid-row: 2; }
}
.ex-result { display: grid; grid-template-columns: auto minmax(0, 1fr); gap: 12px; align-items: start; padding: 14px 16px; border-radius: 10px; background: var(--ok-soft); }
.ex-result .ic { width: 22px; height: 22px; color: var(--ok); margin-top: 2px; }
.ex-result.warn { background: var(--warn-soft); } .ex-result.warn .ic { color: var(--warn); }
.ex-result.bad { background: var(--bad-soft); } .ex-result.bad .ic { color: var(--bad); }
.ex-result b { display: block; }