/* OpenCircuit Academy — a quiet textbook look.
   Literata for headings, Source Sans 3 for reading, IBM Plex Mono for values.
   One accent (copper) plus a teal used only for live signals in the labs. */

/* ============ Tokens ============ */
:root {
  --bg: #fafaf8;
  --surface: #ffffff;
  --surface2: #f1f1ed;
  --fg: #1b1d21;
  --muted: #62676f;
  --line: #e4e4df;
  --accent: #b8561b;
  --accent-strong: #97440f;
  --accent-soft: #f8ede4;
  --signal: #0f7c70;
  --signal-soft: #e4f2ef;
  --accent2: #0f7c70;
  --good: #1f8a3b;
  --good-soft: #e3f3e7;
  --bad: #c0392b;
  --bad-soft: #fbe9e6;
  --warn: #a4640e;
  --warn-soft: #fbf1df;
  --gate: #5a4bb0;
  --gate-soft: #efedf9;
  --electron: #d9861f;
  --code-bg: #17191d;
  --code-head: #202328;
  --code-fg: #e7e7e3;
  --radius: 8px;
  --head: "Literata", Georgia, "Times New Roman", serif;
  --font: "Source Sans 3", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, "SFMono-Regular", Consolas, monospace;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #121315; --surface: #191b1e; --surface2: #202327; --fg: #e8e8e5; --muted: #9ba0a8; --line: #2d3035;
    --accent: #e38a4f; --accent-strong: #f0a36b; --accent-soft: #33251b; --signal: #4cc9b8; --signal-soft: #16302c; --accent2: #4cc9b8;
    --good: #5ccf7c; --good-soft: #15291b; --bad: #ef8074; --bad-soft: #36191a; --warn: #e5b15c; --warn-soft: #33290f;
    --gate: #a99df0; --gate-soft: #231f3b; --electron: #f2b04a;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #121315; --surface: #191b1e; --surface2: #202327; --fg: #e8e8e5; --muted: #9ba0a8; --line: #2d3035;
  --accent: #e38a4f; --accent-strong: #f0a36b; --accent-soft: #33251b; --signal: #4cc9b8; --signal-soft: #16302c; --accent2: #4cc9b8;
  --good: #5ccf7c; --good-soft: #15291b; --bad: #ef8074; --bad-soft: #36191a; --warn: #e5b15c; --warn-soft: #33290f;
  --gate: #a99df0; --gate-soft: #231f3b; --electron: #f2b04a;
  color-scheme: dark;
}

/* ============ Base ============ */
* { box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--bg); color: var(--fg); font: 17px/1.65 var(--font); overflow-x: hidden; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; }
h1, h2, h3, h4 { font-family: var(--head); font-weight: 600; line-height: 1.25; margin: 1.8em 0 .5em; text-wrap: balance; letter-spacing: -.005em; }
h1 { font-size: clamp(1.75rem, 3.6vw, 2.3rem); margin-top: .2em; }
h2 { font-size: 1.4rem; }
h3 { font-size: 1.12rem; }
h4 { font-size: 1rem; }
p, ul, ol { margin: 0 0 1em; }
code { font-family: var(--mono); font-size: .86em; background: var(--surface2); padding: .08em .35em; border-radius: 4px; }
img, svg, canvas { max-width: 100%; }
main { outline: none; min-height: 60vh; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 4px; }
.muted { color: var(--muted); }
.small { font-size: .92rem; }
.center { text-align: center; }
.mono { font-family: var(--mono); }
.narrow { max-width: 780px; margin-left: auto; margin-right: auto; }
.eyebrow { display: inline-block; font: 600 .78rem var(--font); letter-spacing: .08em; text-transform: uppercase; color: var(--muted); }

/* ============ Header ============ */
.readbar { position: fixed; top: 0; left: 0; height: 2px; width: 0; background: var(--accent); z-index: 60; }
.topbar { position: sticky; top: env(safe-area-inset-top, 0px); z-index: 50; display: flex; align-items: center; gap: 1rem; padding: .7rem clamp(16px, 4vw, 40px); background: color-mix(in srgb, var(--bg) 92%, transparent); backdrop-filter: blur(8px); border-bottom: 1px solid var(--line); }
.logo { display: flex; align-items: center; gap: .5rem; font: 600 1.12rem var(--head); color: var(--fg); }
.logo:hover { text-decoration: none; }
.logo b { font-weight: 600; color: var(--accent); }
.logo-mark { width: 24px; height: 24px; flex: none; }
.nav { display: flex; gap: .2rem; margin-left: 1.2rem; }
.nav a { color: var(--muted); padding: .35rem .7rem; border-radius: 6px; font-weight: 500; }
.nav a:hover { color: var(--fg); text-decoration: none; }
.nav a.active { color: var(--fg); background: var(--surface2); }
.top-actions { display: flex; align-items: center; gap: .4rem; }
.icon-btn { width: 36px; height: 36px; border-radius: 6px; border: 1px solid var(--line); background: var(--surface); color: var(--fg); cursor: pointer; display: grid; place-items: center; font-size: 1rem; }
.icon-btn svg { width: 17px; height: 17px; }
.menu-btn, .search-btn { display: none; }

/* Search */
.search-wrap { position: relative; margin-left: auto; width: min(340px, 34vw); display: flex; align-items: center; }
.search-wrap .s-ico { position: absolute; left: .65rem; width: 16px; height: 16px; color: var(--muted); pointer-events: none; }
.search-wrap input { width: 100%; padding: .45rem 2rem .45rem 2.1rem; border: 1px solid var(--line); border-radius: 6px; background: var(--surface); color: var(--fg); font: .95rem var(--font); }
.search-wrap input:focus { outline: 2px solid var(--accent); outline-offset: 0; border-color: transparent; }
.search-wrap kbd { position: absolute; right: .5rem; font: 500 .72rem var(--mono); color: var(--muted); border: 1px solid var(--line); border-radius: 4px; padding: 0 .35rem; background: var(--surface2); }
.q-res { position: absolute; top: calc(100% + 6px); left: auto; right: 0; width: 440px; max-width: 92vw; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: 0 12px 32px rgba(0,0,0,.14); max-height: 70vh; overflow: auto; z-index: 70; padding: .3rem; }
.q-res a { display: grid; grid-template-columns: 4.6rem 1fr; gap: 0 .6rem; padding: .5rem .6rem; border-radius: 6px; color: var(--fg); }
.q-res a:hover, .q-res a.on { background: var(--surface2); text-decoration: none; }
.q-res .rt { grid-row: span 2; font: 600 .7rem var(--font); letter-spacing: .05em; text-transform: uppercase; color: var(--accent); padding-top: .2rem; }
.q-res b { font-weight: 600; }
.q-res small { color: var(--muted); font-size: .84rem; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.q-res .none { margin: 0; padding: .7rem; color: var(--muted); font-size: .92rem; }

/* Breadcrumbs */
.crumbs { display: flex; flex-wrap: wrap; align-items: center; gap: .3rem .45rem; font-size: .88rem; color: var(--muted); margin-bottom: .8rem; }
.crumbs a { color: var(--muted); }
.crumbs a:hover { color: var(--accent); }
.crumbs .sep { opacity: .6; }
.crumbs [aria-current] { color: var(--fg); }
.ring { --p: 0; width: 36px; height: 36px; border-radius: 50%; display: grid; place-items: center; background: conic-gradient(var(--accent) calc(var(--p) * 1%), var(--line) 0); }
.ring span { width: 30px; height: 30px; border-radius: 50%; background: var(--bg); display: grid; place-items: center; font: 600 .6rem var(--mono); color: var(--fg); }
.ring:hover { text-decoration: none; }

/* ============ Buttons ============ */
.btn { display: inline-flex; align-items: center; justify-content: center; gap: .4rem; padding: .55rem 1.05rem; border-radius: 6px; border: 1px solid transparent; font: 600 .98rem var(--font); cursor: pointer; text-align: center; line-height: 1.3; transition: background .15s, border-color .15s; }
.btn:hover { text-decoration: none; }
.btn.primary { background: var(--accent); color: #fff; }
.btn.primary:hover { background: var(--accent-strong); }
:root[data-theme="dark"] .btn.primary { color: #1b1008; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) .btn.primary { color: #1b1008; } }
.btn.ghost { background: transparent; border-color: var(--line); color: var(--fg); }
.btn.ghost:hover { border-color: var(--muted); }
.btn.big { padding: .7rem 1.3rem; font-size: 1.02rem; }
.btn.small { padding: .32rem .7rem; font-size: .88rem; }
.btn small { display: block; font-weight: 400; opacity: .85; font-size: .8rem; }
.btn-row { display: flex; flex-wrap: wrap; gap: .5rem; align-items: center; }
.btn-row.center { justify-content: center; margin-top: 1rem; }

/* ============ Home ============ */
.home { max-width: 980px; margin: 0 auto; padding: 0 16px; }
.intro { padding: clamp(40px, 7vw, 76px) 0 clamp(28px, 4vw, 40px); max-width: 680px; }
.intro h1 { font-size: clamp(2rem, 4.6vw, 2.85rem); line-height: 1.15; margin: .4em 0 .45em; }
.intro p { color: var(--muted); font-size: 1.1rem; max-width: 600px; }
.intro .btn-row { margin-top: 1.4rem; }
.facts { display: flex; flex-wrap: wrap; gap: .35rem 1.4rem; margin-top: 1.6rem; color: var(--muted); font-size: .95rem; }
.facts b { color: var(--fg); font-variant-numeric: tabular-nums; }
.home-sec { padding: 2.4rem 0 .6rem; border-top: 1px solid var(--line); }
.home-sec > header { display: flex; justify-content: space-between; align-items: baseline; gap: 1rem; flex-wrap: wrap; margin-bottom: .6rem; }
.home-sec h2 { margin: 0; }
.home-sec > header a { font-weight: 600; }
.mod-list { list-style: none; padding: 0; margin: 0; }
.mod-list li { border-bottom: 1px solid var(--line); }
.mod-list li:last-child { border-bottom: 0; }
.mod-list a { display: grid; grid-template-columns: 2.4rem 1fr auto; gap: .2rem 1rem; align-items: baseline; padding: .95rem .2rem; color: var(--fg); }
.mod-list a:hover { text-decoration: none; background: var(--surface2); }
.mod-list .n { font: 500 .9rem var(--mono); color: var(--muted); }
.mod-list .t { font: 600 1.08rem var(--head); }
.mod-list .d { grid-column: 2; color: var(--muted); font-size: .96rem; }
.mod-list .s { grid-column: 3; grid-row: 1; font-size: .88rem; color: var(--muted); white-space: nowrap; }
.mod-list .s.done { color: var(--good); font-weight: 600; }
.feature-projects { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; margin-top: .6rem; }
.fp { display: block; padding: 1rem 1.1rem; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); color: var(--fg); }
.fp:hover { border-color: var(--accent); text-decoration: none; }
.fp b { display: block; font: 600 1.02rem var(--head); margin: .3rem 0 .2rem; }
.fp span { font-size: .9rem; color: var(--muted); }
.how { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.2rem 2rem; margin-top: .6rem; }
.how h3 { margin: 0 0 .25rem; font-size: 1.02rem; }
.how p { margin: 0; color: var(--muted); font-size: .96rem; }

/* Home: resume card and start-here path */
.resume { display: grid; gap: .2rem; padding: 1.1rem 1.3rem; margin: 0 0 1.4rem; border: 1px solid color-mix(in srgb, var(--accent) 45%, var(--line)); border-radius: var(--radius); background: var(--accent-soft); color: var(--fg); max-width: 640px; }
.resume:hover { text-decoration: none; border-color: var(--accent); }
.resume .eyebrow { color: var(--accent-strong); }
.resume b { font: 600 1.25rem var(--head); }
.resume small { color: var(--muted); }
.resume-bar { height: 4px; background: var(--line); border-radius: 2px; overflow: hidden; margin: .5rem 0 .1rem; }
.resume-bar i { display: block; height: 100%; background: var(--accent); }
.start { padding: 1.4rem 0 2rem; border-top: 1px solid var(--line); }
.start h2 { margin: 0 0 1rem; }
.start-steps { list-style: none; padding: 0; margin: 0 0 1.2rem; display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.4rem; }
.start-steps li { display: grid; grid-template-columns: 2rem 1fr; gap: .7rem; }
.start-steps li > span { width: 2rem; height: 2rem; border-radius: 50%; background: var(--accent); color: #fff; display: grid; place-items: center; font-weight: 700; }
.start-steps b { font: 600 1.02rem var(--head); }
.start-steps p { margin: .2rem 0 0; color: var(--muted); font-size: .94rem; }

/* Branch cards (home) */
.branch-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 0 2rem; margin-top: .4rem; }
.branch { display: grid; grid-template-columns: 2.2rem 1fr; gap: .15rem .8rem; padding: 1rem .2rem; border-bottom: 1px solid var(--line); color: var(--fg); }
.branch:hover { text-decoration: none; background: var(--surface2); }
.branch .n { grid-row: span 3; font: 500 .9rem var(--mono); color: var(--muted); padding-top: .15rem; }
.branch b { font: 600 1.1rem var(--head); }
.branch .d { color: var(--muted); font-size: .95rem; }
.branch .meta { font-size: .84rem; color: var(--muted); }
.branch .prog { grid-column: 2; height: 3px; background: var(--line); border-radius: 2px; overflow: hidden; margin-top: .3rem; }
.branch .prog i { display: block; height: 100%; background: var(--accent); }
.cat-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 12px; margin-top: .6rem; }
.cat-card { display: flex; flex-direction: column; gap: .2rem; padding: 1rem 1.1rem; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); color: var(--fg); }
.cat-card:hover { border-color: var(--accent); text-decoration: none; }
.cat-card b { font: 600 1.05rem var(--head); }
.cat-card .n { font-size: .85rem; color: var(--accent); font-weight: 600; }
.cat-card span:last-child { font-size: .9rem; color: var(--muted); }

/* Learn page: branches with their modules */
.tracks { max-width: 980px; margin: 0 auto; padding: 0 16px 3rem; }
.track-row { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.25fr); gap: 1rem 2.4rem; padding: 1.4rem 0; border-top: 1px solid var(--line); }
.track-head { display: grid; grid-template-columns: 2.2rem 1fr; gap: .8rem; }
.track-head .n { font: 500 .9rem var(--mono); color: var(--muted); padding-top: .3rem; }
.track-head h2 { margin: 0 0 .25rem; font-size: 1.25rem; }
.track-head h2 a { color: var(--fg); }
.track-head p { margin: 0; color: var(--muted); font-size: .95rem; }
.track-mods { list-style: none; padding: 0; margin: 0; }
.track-mods a { display: flex; align-items: center; gap: .6rem; padding: .45rem .2rem; color: var(--fg); border-bottom: 1px solid var(--line); }
.track-mods li:last-child a { border-bottom: 0; }
.track-mods a:hover { color: var(--accent); text-decoration: none; }
.track-mods .t { flex: 1; }
.lvl { font-size: .78rem; color: var(--muted); white-space: nowrap; }
.track-mods small { color: var(--muted); font-size: .82rem; min-width: 2.2rem; text-align: right; }

/* Branch page */
.t-facts { display: flex; flex-wrap: wrap; gap: .4rem 1.4rem; font-size: .94rem; color: var(--muted); margin-top: .6rem; }
.t-facts b { color: var(--fg); }
.jump { display: flex; flex-wrap: wrap; gap: .4rem; margin-top: 1.2rem; }
.jump a { padding: .3rem .8rem; border: 1px solid var(--line); border-radius: 999px; font-size: .9rem; color: var(--fg); background: var(--surface); }
.jump a:hover { border-color: var(--accent); text-decoration: none; }
.track-page h2 { scroll-margin-top: 80px; }
.checks-list { list-style: none; padding: 0; display: grid; gap: .4rem; }
.checks-list li { position: relative; padding-left: 1.7rem; }
.checks-list li::before { content: "✓"; position: absolute; left: 0; top: .05rem; width: 1.2rem; height: 1.2rem; border-radius: 50%; background: var(--good-soft); color: var(--good); display: grid; place-items: center; font-size: .75rem; font-weight: 700; }
.day { padding: 1rem 1.2rem; background: var(--surface2); border-radius: var(--radius); margin-bottom: 1.2rem; }
.day p { margin: .25rem 0 0; }
.interview { columns: 2; column-gap: 2rem; padding-left: 1.3rem; }
.interview li { break-inside: avoid; margin-bottom: .35rem; }
.track-page { padding: 0 16px 3rem; }
.uses { columns: 2; column-gap: 2rem; padding-left: 1.1rem; }
.path { list-style: none; padding: 0; margin: 1rem 0 1.4rem; }
.path > li { display: grid; grid-template-columns: 2.2rem 1fr; gap: 1rem; padding: 1rem 0; border-top: 1px solid var(--line); }
.path .step { width: 2rem; height: 2rem; border-radius: 50%; background: var(--surface2); display: grid; place-items: center; font: 600 .9rem var(--mono); }
.path > li.done .step { background: var(--good); color: #fff; }
.path b { font: 600 1.08rem var(--head); color: var(--fg); }
.path p { margin: .2rem 0 .4rem; color: var(--muted); font-size: .95rem; }
.path-lessons { list-style: none; padding: 0; margin: 0; display: grid; grid-template-columns: 1fr 1fr; gap: 0 1rem; }
.path-lessons a { display: flex; gap: .5rem; align-items: flex-start; padding: .2rem 0; font-size: .93rem; color: var(--fg); }
.industry { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem 2rem; }
.industry h3 { margin: 0 0 .3rem; font-size: 1rem; }
.industry ul { padding-left: 1.1rem; margin: 0; }
.proj-grid.inline { padding: 0; max-width: none; }
.track-nav { display: flex; justify-content: space-between; margin-top: 2.4rem; padding-top: 1rem; border-top: 1px solid var(--line); font-weight: 600; }

/* ============ Page heads & curriculum ============ */
.page-head { max-width: 980px; margin: 0 auto; padding: 2.4rem 16px 1rem; }
.page-head h1 { margin-bottom: .3rem; }
.page-head p { color: var(--muted); max-width: 66ch; }
.page-head.narrow { max-width: 780px; }
.crumb { display: block; width: fit-content; font-size: .92rem; margin-bottom: .5rem; color: var(--muted); }
.bar { height: 4px; background: var(--line); border-radius: 2px; overflow: hidden; margin: 1rem 0 .4rem; max-width: 420px; }
.bar div { height: 100%; background: var(--accent); transition: width .5s; }
.modules { max-width: 980px; margin: 0 auto; padding: 0 16px 3rem; display: grid; grid-template-columns: 1fr 1fr; gap: 2rem 2.4rem; }
.module-card h2 { margin: .2rem 0 .25rem; font-size: 1.2rem; }
.module-card h2 a { color: var(--fg); }
.module-card > p { color: var(--muted); font-size: .95rem; margin: 0 0 .4rem; }
.m-num { font: 600 .78rem var(--font); letter-spacing: .06em; text-transform: uppercase; color: var(--muted); }
.m-hero { display: flex; gap: 1.1rem; align-items: center; }
.m-hero h1 { margin: .15rem 0; }
.m-hero p { margin: 0; }
.des-badge { flex: none; width: 56px; height: 56px; border-radius: 8px; background: var(--accent-soft); color: var(--accent); display: grid; place-items: center; font: 600 1.2rem var(--mono); }
.lesson-list { list-style: none; padding: 0; margin: .3rem 0 0; }
.lesson-list li a { display: flex; align-items: center; gap: .6rem; padding: .38rem .2rem; color: var(--fg); font-size: .97rem; }
.lesson-list li a:hover { color: var(--accent); text-decoration: none; }
.lesson-list small { margin-left: auto; color: var(--muted); white-space: nowrap; font-size: .82rem; }
.lesson-list.big { max-width: 780px; margin: 0 auto 2rem; padding: 0 16px; }
.lesson-list.big li { border-bottom: 1px solid var(--line); }
.lesson-list.big li a { padding: .85rem .2rem; font-size: 1.02rem; align-items: flex-start; }
.ln { width: 1.6rem; flex: none; font: 500 .88rem var(--mono); color: var(--muted); padding-top: .1rem; }
.quiz-li a { font-weight: 600; }
.chk { flex: none; width: 16px; height: 16px; border-radius: 50%; border: 1.5px solid var(--line); display: grid; place-items: center; font-size: .6rem; margin-top: .05rem; }
li.done > a .chk, li.done > .chk { background: var(--good); border-color: var(--good); }
li.done > a .chk::after, li.done > .chk::after { content: "✓"; color: #fff; font-weight: 700; }

/* ============ Lesson ============ */
.lesson-layout { max-width: 1280px; margin: 0 auto; display: grid; grid-template-columns: 260px minmax(0, 1fr) 190px; gap: 3rem; padding: 1.6rem 16px 3rem; }
.side, .toc { position: sticky; top: 76px; align-self: start; max-height: calc(100vh - 96px); overflow: auto; }
.side h3 { margin: 0 0 .7rem; font-size: 1rem; }
.side-head { display: flex; justify-content: space-between; align-items: center; margin-bottom: .5rem; }
.side-head b { font: 600 1rem var(--head); }
.side-close, .map-btn { display: none; }
.map details summary { list-style: none; cursor: pointer; }
.map details summary::-webkit-details-marker { display: none; }
.map-branch { border-bottom: 1px solid var(--line); }
.map-branch > summary { display: flex; justify-content: space-between; align-items: center; gap: .5rem; padding: .55rem .2rem; font-weight: 600; font-size: .95rem; }
.map-branch > summary::before { content: "▸"; color: var(--muted); font-size: .75rem; transition: transform .15s; }
.map-branch[open] > summary::before { transform: rotate(90deg); }
.map-branch > summary span { flex: 1; }
.map-branch > summary small { color: var(--muted); font-weight: 400; font-size: .78rem; }
.map-mod { margin: 0 0 .3rem .7rem; }
.map-mod > summary { display: flex; align-items: flex-start; gap: .45rem; padding: .3rem .2rem; font-size: .9rem; color: var(--fg); line-height: 1.35; }
.map-mod > summary .chk { width: 12px; height: 12px; margin-top: .2rem; }
.map-mod > summary.done .chk { background: var(--good); border-color: var(--good); }
.map-mod ol { list-style: none; padding: 0 0 .3rem 1.1rem; margin: 0; }
.map-mod li a { display: flex; gap: .45rem; align-items: flex-start; padding: .25rem .4rem; border-radius: 5px; color: var(--muted); font-size: .86rem; line-height: 1.35; }
.map-mod li a:hover { color: var(--fg); text-decoration: none; }
.map-mod li.cur a { background: var(--accent-soft); color: var(--accent-strong); font-weight: 600; }
.map-mod li .chk { width: 12px; height: 12px; margin-top: .15rem; }
.map-scrim { display: none; }
.side-list { list-style: none; padding: 0; margin: 0; }
.side-list a { display: flex; gap: .5rem; align-items: flex-start; padding: .35rem .4rem; border-radius: 5px; color: var(--muted); font-size: .93rem; line-height: 1.35; }
.side-list a:hover { color: var(--fg); text-decoration: none; }
.side-list li.cur a { color: var(--fg); font-weight: 600; background: var(--surface2); }
.toc { padding-left: .2rem; }
.toc .eyebrow { display: block; margin-bottom: .5rem; }
.toc a { display: block; font-size: .88rem; color: var(--muted); padding: .25rem 0 .25rem .7rem; border-left: 2px solid var(--line); line-height: 1.35; }
.toc a:hover { color: var(--fg); text-decoration: none; }
.toc a.on { color: var(--fg); border-left-color: var(--accent); }
.lesson { min-width: 0; max-width: 700px; }
.lesson.solo { margin: 0 auto; padding: 2rem 16px 3rem; max-width: 780px; }
.lesson-meta { font-size: .9rem; color: var(--muted); display: flex; gap: .4rem; flex-wrap: wrap; }
.lesson-meta span + span::before { content: "·"; margin-right: .4rem; }
.lead { font-size: 1.14rem; line-height: 1.6; }
.lesson ul li, .lesson ol li { margin-bottom: .3rem; }
.lesson h2 { scroll-margin-top: 76px; }
.big-idea { margin: .8rem 0 1.8rem; padding-left: 1rem; border-left: 3px solid var(--accent); }
.big-idea .eyebrow { color: var(--accent); }
.big-idea p { margin: .15rem 0 0; font: 500 1.15rem/1.5 var(--head); }
.recap { margin: 2.6rem 0 0; padding: 1.1rem 1.3rem; background: var(--surface2); border-radius: var(--radius); }
.recap-head { font: 600 1rem var(--head); margin-bottom: .3rem; }
.recap ol { margin: 0; padding-left: 1.3rem; }
.recap li { padding: .2rem 0; }
.lesson-nav { display: flex; justify-content: space-between; gap: 1rem; margin-top: 2rem; flex-wrap: wrap; }
.mod-progress { display: flex; gap: 4px; margin: .5rem 0 .2rem; max-width: 320px; }
.mod-progress i { flex: 1; height: 4px; border-radius: 2px; background: var(--line); }
.mod-progress i.done { background: var(--good); }
.mod-progress i.cur { background: var(--accent); }
.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 2.2rem; }
.pg { display: flex; flex-direction: column; gap: .1rem; padding: .8rem 1rem; border: 1px solid var(--line); border-radius: var(--radius); color: var(--fg); background: var(--surface); }
.pg:hover { border-color: var(--accent); text-decoration: none; }
.pg small { color: var(--muted); font-size: .84rem; }
.pg b { font: 600 1rem var(--head); }
.pg.next { text-align: right; border-color: color-mix(in srgb, var(--accent) 45%, var(--line)); }

/* Practice problems */
.practice { margin-top: 2.2rem; }
.prob { border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); margin: .6rem 0; }
.prob summary { display: flex; gap: .7rem; padding: .8rem 1rem; cursor: pointer; list-style: none; font-weight: 500; }
.prob summary::-webkit-details-marker { display: none; }
.prob summary::after { content: "Show solution"; margin-left: auto; flex: none; font-size: .82rem; color: var(--accent); font-weight: 600; align-self: center; }
.prob[open] summary::after { content: "Hide"; }
.prob .qn { flex: none; font: 600 .85rem var(--mono); color: var(--accent); padding-top: .12rem; }
.prob .sol { padding: .1rem 1rem 1rem 2.9rem; border-top: 1px dashed var(--line); }
.prob .sol .eyebrow { display: block; margin: .7rem 0 .2rem; color: var(--good); }

/* Callouts: one quiet style, tinted by purpose */
.callout { border-radius: var(--radius); padding: .9rem 1.1rem; margin: 1.4rem 0; background: var(--surface2); }
.callout p:last-child { margin-bottom: 0; }
.callout-title { font: 600 .98rem var(--font); margin-bottom: .25rem; }
.callout.analogy { background: var(--accent-soft); }
.callout.analogy .callout-title { color: var(--accent-strong); }
.callout.key .callout-title { color: var(--fg); }
.callout.mistake { background: var(--bad-soft); }
.callout.mistake .callout-title { color: var(--bad); }
.callout.gate { background: var(--gate-soft); }
.callout.gate .callout-title { color: var(--gate); }
.callout.fact { background: var(--good-soft); }
.callout.fact .callout-title { color: var(--good); }

.formula { text-align: center; margin: 1.3rem 0; padding: .9rem; }
.formula-main { display: inline-block; font: 500 clamp(1.15rem, 3vw, 1.45rem) var(--mono); color: var(--fg); padding: .35rem 1rem; border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.formula-cap { color: var(--muted); font-size: .92rem; margin-top: .4rem; }
.figure { margin: 1.4rem 0; text-align: center; padding: .6rem 0; }
.figure svg { max-height: 280px; width: 100%; }
figcaption { font-size: .9rem; color: var(--muted); margin-top: .4rem; }
.steps { counter-reset: s; list-style: none; padding: 0; margin: 1rem 0; }
.steps li { counter-increment: s; position: relative; padding: .5rem 0 .5rem 2.3rem; border-bottom: 1px solid var(--line); margin: 0; }
.steps li:last-child { border-bottom: 0; }
.steps li::before { content: counter(s); position: absolute; left: 0; top: .55rem; width: 1.5rem; height: 1.5rem; border-radius: 50%; background: var(--surface2); display: grid; place-items: center; font: 600 .8rem var(--mono); color: var(--fg); }
.table-wrap { overflow-x: auto; margin: 1.2rem 0; }
table { width: 100%; border-collapse: collapse; font-size: .95rem; }
th, td { padding: .55rem .7rem; text-align: left; border-bottom: 1px solid var(--line); vertical-align: top; }
th { font-weight: 600; color: var(--fg); border-bottom: 2px solid var(--line); }
td { font-variant-numeric: tabular-nums; }
.trio { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.4rem; margin: 1.4rem 0; }
.trio-card h4 { margin: .2rem 0 .2rem; }
.trio-card p { font-size: .95rem; color: var(--muted); margin: 0 0 .3rem; }
.trio-sym { font: 600 1.8rem var(--head); color: var(--accent); line-height: 1; }
.unit { font: 500 .8rem var(--mono); color: var(--muted); }
.compare { display: grid; grid-template-columns: 1fr 1fr; gap: 1.6rem; margin: 1.4rem 0; }
.compare > div { min-width: 0; }
.compare h3, .compare h4 { margin-top: 0; }
.compare ul { padding-left: 1.1rem; margin: 0; font-size: .96rem; }
.compare svg { width: 100%; height: auto; max-height: 100px; margin-bottom: .4rem; }
.mnemonic { text-align: center; font-size: 1.05rem; padding: .6rem; background: var(--surface2); border-radius: var(--radius); }
.colorcode { display: grid; grid-template-columns: repeat(5, 1fr); gap: 4px 12px; margin: 1rem 0; }
.cc { display: flex; align-items: center; gap: .45rem; font-size: .9rem; padding: .2rem 0; }
.cc span { width: 16px; height: 16px; border-radius: 3px; border: 1px solid var(--line); flex: none; }
.cc b { font-family: var(--mono); }
.cc small { color: var(--muted); }
.symbols { display: grid; grid-template-columns: repeat(auto-fill, minmax(130px, 1fr)); gap: 1rem; margin: 1.2rem 0; }
.symbols figure { margin: 0; text-align: center; }
.symbols svg { height: 46px; overflow: visible; }
.chips { display: flex; flex-wrap: wrap; gap: .4rem; margin: 1rem 0 1.4rem; }
.chips span { padding: .2rem .65rem; background: var(--surface2); border-radius: 999px; font-size: .92rem; }
.flow-diagram { display: flex; align-items: stretch; gap: .5rem; margin: 1.2rem 0; flex-wrap: wrap; justify-content: center; }
.flow-diagram .node { flex: 1; min-width: 140px; background: var(--surface2); border-radius: var(--radius); padding: .8rem; text-align: center; font-weight: 600; }
.flow-diagram .node.hl { background: var(--accent-soft); color: var(--accent-strong); }
.flow-diagram small { display: block; font-weight: 400; font-size: .85rem; color: var(--muted); }
.flow-diagram .arrow { align-self: center; color: var(--muted); }
.timeline { border-left: 2px solid var(--line); margin: 1.2rem 0 1.5rem .4rem; padding-left: 1.2rem; }
.t-item { position: relative; margin-bottom: .9rem; }
.t-item::before { content: ""; position: absolute; left: calc(-1.2rem - 6px); top: .55rem; width: 10px; height: 10px; border-radius: 50%; background: var(--accent); }
.t-item p { margin: 0; color: var(--muted); font-size: .95rem; }

/* Code */
.code { margin: 1.2rem 0; border-radius: var(--radius); overflow: hidden; background: var(--code-bg); }
.code-head { display: flex; justify-content: space-between; align-items: center; padding: .35rem .8rem; background: var(--code-head); color: #9ca3ad; font: 500 .74rem var(--mono); }
.copy { background: transparent; border: 1px solid #353a42; color: #d6d6d2; border-radius: 4px; font: 500 .74rem var(--font); padding: .15rem .55rem; cursor: pointer; }
.copy:hover { border-color: #6b727c; }
.code pre { margin: 0; padding: .95rem 1rem; overflow-x: auto; }
.code code { background: none; padding: 0; color: var(--code-fg); font-size: .86rem; line-height: 1.6; }
.code .c-com { color: #8a929c; font-style: italic; }
.code .c-str { color: #e9b98a; }
.code .c-kw { color: #86c9d6; }
.code .c-num { color: #d9c47e; }

/* ============ Labs / widgets ============ */
.lab { margin: 1.8rem 0; border-radius: var(--radius); border: 1px solid var(--line); background: var(--surface); }
.lab-head { display: flex; align-items: center; gap: .6rem; padding: .6rem 1rem; border-bottom: 1px solid var(--line); }
.lab-head h3 { margin: 0; font: 600 .98rem var(--font); }
.lab-badge { font: 600 .72rem var(--font); letter-spacing: .06em; text-transform: uppercase; color: var(--signal); background: var(--signal-soft); padding: .12rem .5rem; border-radius: 4px; }
.widget { padding: 1rem; }
.w-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem 1.4rem; align-items: center; }
.w-grid.three { grid-template-columns: repeat(3, 1fr); }
.w-grid.four { grid-template-columns: repeat(4, 1fr); }
.ctl { display: block; margin-bottom: .7rem; }
.ctl > span { display: flex; justify-content: space-between; gap: .5rem; font-size: .9rem; font-weight: 600; margin-bottom: .25rem; }
.ctl output { color: var(--signal); font-family: var(--mono); font-weight: 500; }
.ctl input[type=range] { width: 100%; accent-color: var(--accent); }
.ctl select, .ctl.num input, .search { width: 100%; padding: .5rem .65rem; border-radius: 6px; border: 1px solid var(--line); background: var(--bg); color: var(--fg); font: 1rem var(--font); }
.ctl.num input:disabled { opacity: 1; background: var(--signal-soft); color: var(--signal); font-weight: 700; }
.ctl.inline { max-width: 320px; }
.ctl.solved > span { color: var(--signal); }
.readout { display: flex; flex-wrap: wrap; gap: 8px; margin-top: .6rem; }
.readout > div { flex: 1; min-width: 120px; background: var(--surface2); border-radius: 6px; padding: .45rem .75rem; }
.readout small { display: block; color: var(--muted); font-size: .8rem; }
.readout b { font: 600 1.05rem var(--mono); color: var(--fg); word-break: break-all; font-variant-numeric: tabular-nums; }
.readout.big b { font-size: 1.2rem; color: var(--signal); }
.w-note { font-size: .92rem; color: var(--muted); margin: .7rem 0 0; }
.w-note.center { text-align: center; }
.seg { display: inline-flex; background: var(--surface2); border-radius: 6px; padding: 3px; gap: 2px; margin-bottom: 1rem; }
.seg.wrap { flex-wrap: wrap; }
.seg button { border: 0; background: transparent; padding: .32rem .75rem; border-radius: 4px; font: 600 .88rem var(--font); color: var(--muted); cursor: pointer; }
.seg button.on { background: var(--surface); color: var(--fg); box-shadow: 0 1px 2px rgba(0,0,0,.08); }
.plot { width: 100%; height: 230px; display: block; margin: .6rem 0; background: var(--bg); border-radius: 6px; border: 1px solid var(--line); }
.plot.short { height: 150px; }
.flow-svg { width: 100%; max-height: 210px; }
.cc-svg { width: 100%; max-height: 90px; margin-bottom: .8rem; }

.led-stage { display: grid; place-items: center; gap: .6rem; min-height: 130px; }
.led-bulb { --glow: .6; --led: #ff3b3b; width: 64px; height: 84px; border-radius: 32px 32px 10px 10px; background: color-mix(in srgb, var(--led) calc(25% + var(--glow) * 75%), #333); box-shadow: 0 0 calc(var(--glow) * 44px) calc(var(--glow) * 14px) color-mix(in srgb, var(--led) calc(var(--glow) * 75%), transparent); transition: all .2s; }
.lamp { --glow: 0; font-size: 3.6rem; filter: grayscale(calc(1 - var(--glow))) brightness(calc(.6 + var(--glow) * .6)) drop-shadow(0 0 calc(var(--glow) * 20px) #fbbf24); transition: filter .2s; }
.region { font-size: .88rem; font-weight: 600; padding: .25rem .75rem; border-radius: 99px; background: var(--surface2); }
.region[data-state=sat] { background: var(--good-soft); color: var(--good); }
.region[data-state=act] { background: var(--warn-soft); color: var(--warn); }
.region[data-state=off] { background: var(--bad-soft); color: var(--bad); }
.meter-col { display: grid; place-items: center; }
.vbar { position: relative; width: 64px; height: 170px; border-radius: 6px; background: var(--surface2); overflow: hidden; }
.vbar-fill { position: absolute; bottom: 0; left: 0; right: 0; background: var(--signal); transition: height .15s; }
.vbar-label { position: absolute; left: 0; right: 0; top: 6px; text-align: center; font: 600 .72rem var(--mono); color: var(--fg); }

.bits { display: grid; grid-template-columns: repeat(8, 1fr); gap: 5px; margin-bottom: .8rem; }
.bit { display: flex; flex-direction: column; align-items: center; justify-content: center; padding: .55rem 0; border-radius: 6px; border: 1px solid var(--line); background: var(--surface2); font: 600 1.3rem var(--mono); color: var(--muted); cursor: pointer; transition: all .15s; }
button.bit:hover { border-color: var(--accent); }
.bit small { font: 500 .66rem var(--mono); color: var(--muted); }
.bit.on { background: var(--signal); border-color: var(--signal); color: #fff; }
.bit.on small { color: rgba(255,255,255,.85); }
.bits.small .bit { font-size: 1.05rem; cursor: default; }
.bits.small .bit small { font-size: .56rem; }

.gate-stage { display: grid; grid-template-columns: auto 1fr auto; align-items: center; gap: 1rem; margin: .4rem 0 1rem; }
.gate-inputs { display: flex; flex-direction: column; gap: .7rem; }
.toggle { border: 1px solid var(--line); background: var(--surface2); color: var(--fg); padding: .45rem .85rem; border-radius: 6px; font: 600 .92rem var(--mono); cursor: pointer; min-width: 78px; }
.toggle.on { background: var(--signal); border-color: var(--signal); color: #fff; }
.toggle.big { font-size: 1.02rem; padding: .6rem 1.1rem; }
.gate-svg { width: 100%; max-height: 115px; }
.gate-shape path, .gate-shape circle { fill: var(--surface2); stroke: var(--fg); stroke-width: 3; }
.gate-shape line { stroke: var(--fg); stroke-width: 3; }
.gate-out { display: flex; flex-direction: column; align-items: center; gap: .3rem; font: 600 .98rem var(--mono); }
.gate-out.col { gap: .8rem; }
.gate-out.col > div { display: flex; align-items: center; gap: .5rem; }
.out-led { width: 32px; height: 32px; border-radius: 50%; background: var(--line); border: 2px solid var(--muted); transition: all .15s; }
.out-led.on { background: #ff4040; border-color: #ff4040; box-shadow: 0 0 16px 4px rgba(255, 64, 64, .5); }
.out-led.alt.on { background: var(--electron); border-color: var(--electron); box-shadow: 0 0 16px 4px color-mix(in srgb, var(--electron) 50%, transparent); }
.out-led.big { width: 60px; height: 60px; }
.tt { max-width: 300px; margin: 0 auto; text-align: center; }
.tt th, .tt td { text-align: center; }
.tt tr.cur td { background: var(--signal-soft); color: var(--signal); font-weight: 700; }
.adder-mid { display: flex; flex-direction: column; gap: .6rem; align-items: center; }
.chip-box { padding: .45rem .9rem; background: var(--surface2); border: 1px solid var(--line); border-radius: 6px; font: 600 .88rem var(--mono); }

.board-mini { display: grid; place-items: center; gap: .5rem; padding: 1rem; background: #0f6f7a; border-radius: var(--radius); color: #fff; }
.board-mini small { color: #e0f7fa; text-align: center; }
.pin13 { font: 600 .8rem var(--mono); background: #111; padding: .15rem .5rem; border-radius: 4px; }
.adc-bar { position: relative; height: 22px; background: var(--surface2); border-radius: 4px; overflow: hidden; margin: .4rem 0; }
.adc-bar > div { height: 100%; background: var(--signal); }
.adc-bar span { position: absolute; top: 0; bottom: 0; width: 1px; background: color-mix(in srgb, var(--fg) 20%, transparent); }
.reg-row { display: flex; align-items: center; gap: .8rem; margin-bottom: .8rem; }
.reg-row .bits { flex: 1; margin: 0; }
.reg-name { font: 600 .98rem var(--mono); color: var(--accent); }
.code-line { background: var(--code-bg); color: var(--code-fg); padding: .65rem 1rem; border-radius: 6px; font-size: .88rem; margin: .6rem 0; overflow-x: auto; white-space: pre; }
.reg-led { display: flex; align-items: center; gap: .6rem; font-size: .92rem; color: var(--muted); }
.uart-wrap { overflow-x: auto; margin: .6rem 0; }
.uart-svg { min-width: 560px; width: 100%; }
.cmos-wrap { display: grid; grid-template-columns: auto 1fr auto; gap: 1rem; align-items: center; }
.cmos-svg { max-height: 290px; width: 100%; }
.tr-on { fill: var(--good-soft); stroke: var(--good); stroke-width: 3; }
.tr-off { fill: var(--surface2); stroke: var(--muted); stroke-width: 2; stroke-dasharray: 5 4; }
.checks { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 6px; margin-bottom: 1rem; }
.check { display: flex; gap: .5rem; align-items: center; padding: .45rem .65rem; border: 1px solid var(--line); border-radius: 6px; cursor: pointer; font-size: .94rem; }
.check:has(input:checked) { border-color: var(--signal); background: var(--signal-soft); }
.check input { accent-color: var(--signal); }
.pick-results { display: grid; gap: 6px; }
.pick { padding: .6rem .8rem; border-radius: 6px; background: var(--surface2); }
.pick.best { background: var(--signal-soft); }
.pick-top { display: flex; align-items: center; gap: .6rem; }
.pill-best { font: 600 .72rem var(--font); letter-spacing: .05em; text-transform: uppercase; color: var(--signal); }
.pick-bar { height: 4px; background: var(--line); border-radius: 2px; margin: .4rem 0 .3rem; overflow: hidden; }
.pick-bar i { display: block; height: 100%; background: var(--signal); }
.pick small { color: var(--muted); }

/* SVG utility classes */
.stroke-muted { stroke: var(--muted); }
.stroke-accent { stroke: var(--accent); }
.stroke-accent2 { stroke: var(--signal); }
.stroke-fg { stroke: var(--fg); }
.fill-accent { fill: var(--accent); }
.fill-accent2 { fill: var(--signal); }
.fill-soft { fill: var(--accent-soft); }
.fill-muted { fill: var(--muted); }
.fill-fg { fill: var(--fg); }
.fill-electron { fill: var(--electron); }
.fill-none { fill: none; }
.svg-label { fill: var(--fg); font: 600 15px var(--font); }
.svg-small { fill: var(--muted); font: 12px var(--font); }
.svg-big { fill: var(--fg); font: 600 34px var(--head); }
.svg-label-inv { fill: #fff; font: 700 18px var(--font); }
.svg-small-inv { fill: #fff; font: 700 12px var(--font); }
.spin { animation: spin 4s linear infinite; }
.spin.slow { animation-duration: 7s; animation-direction: reverse; }
@keyframes spin { to { transform: rotate(360deg); } }

/* ============ Quiz ============ */
.quiz { padding: 0 16px 3rem; }
.q { border: 0; border-bottom: 1px solid var(--line); padding: 1.1rem 0 1.3rem; margin: 0; }
.q legend { font: 600 1.05rem var(--head); padding: 0; margin-bottom: .6rem; float: left; width: 100%; }
.qn { font: 500 .88rem var(--mono); color: var(--muted); margin-right: .5rem; }
.opts { clear: both; display: grid; gap: 6px; }
.opt { display: flex; gap: .6rem; align-items: center; padding: .5rem .75rem; border: 1px solid var(--line); border-radius: 6px; cursor: pointer; background: var(--surface); }
.opt:hover { border-color: var(--muted); }
.opt input { accent-color: var(--accent); }
.opt.is-answer { border-color: var(--good); background: var(--good-soft); }
.opt.is-wrong { border-color: var(--bad); background: var(--bad-soft); }
.q.missing legend { color: var(--warn); }
.why { margin-top: .6rem; font-size: .96rem; color: var(--muted); }
.quiz-foot { text-align: center; margin: 1.5rem 0; }
.result { text-align: center; padding: 1.5rem 1.2rem; border-radius: var(--radius); margin-top: 1rem; }
.result h2 { margin: .2rem 0; }
.result.pass { background: var(--good-soft); }
.result.fail { background: var(--warn-soft); }
.result.warn { background: var(--warn-soft); padding: .8rem; }
.big-emoji { font-size: 2.2rem; }

/* ============ Projects ============ */
.cat-tabs { max-width: 980px; margin: 0 auto; padding: 0 16px; display: flex; gap: .2rem; border-bottom: 1px solid var(--line); overflow-x: auto; }
.cat-tabs button { border: 0; background: none; padding: .6rem .9rem; font: 600 1rem var(--font); color: var(--muted); cursor: pointer; border-bottom: 2px solid transparent; margin-bottom: -1px; white-space: nowrap; }
.cat-tabs button small { font-weight: 500; opacity: .8; }
.cat-tabs button.on { color: var(--fg); border-bottom-color: var(--accent); }
.cat-desc { max-width: 980px; margin: .9rem auto .6rem; padding: 0 16px; color: var(--muted); }
.tags { display: flex; gap: .6rem; align-items: center; flex-wrap: wrap; }
.cat-tag { font-size: .78rem; color: var(--muted); }
.filters { max-width: 980px; margin: 0 auto; padding: 0 16px 1.2rem; display: grid; gap: .5rem; }
.filter-row { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; }
.filter-row > span { font-size: .9rem; color: var(--muted); width: 72px; }
.fchip { border: 1px solid var(--line); background: transparent; color: var(--fg); padding: .25rem .7rem; border-radius: 999px; font: 500 .92rem var(--font); cursor: pointer; }
.fchip small { color: var(--muted); margin-left: .25rem; }
.fchip.on { background: var(--fg); color: var(--bg); border-color: var(--fg); }
.fchip.on small { color: inherit; opacity: .7; }
.proj-count { font-size: .9rem; color: var(--muted); margin-left: .4rem; }
.proj-grid { max-width: 980px; margin: 0 auto; padding: 0 16px 3rem; display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 12px; }
.proj-card { display: flex; flex-direction: column; padding: 1rem 1.1rem; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); color: var(--fg); }
.proj-card:hover { text-decoration: none; border-color: var(--accent); }
.proj-card h3 { margin: .45rem 0 .3rem; font-size: 1.08rem; }
.proj-card p { color: var(--muted); font-size: .93rem; margin: 0 0 .8rem; flex: 1; }
.plat { display: inline-block; font: 600 .74rem var(--font); letter-spacing: .04em; text-transform: uppercase; color: var(--muted); }
.plat.arduino { color: #0b7b86; }
.plat.esp32 { color: #b8561b; }
.plat.pico { color: #4d7f1a; }
.plat.raspi { color: #b1224f; }
.plat.analog { color: #5a4bb0; }
:root[data-theme="dark"] .plat { filter: brightness(1.5); }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) .plat { filter: brightness(1.5); } }
.p-meta { display: flex; gap: .9rem; font-size: .86rem; color: var(--muted); align-items: center; flex-wrap: wrap; }
.diff-meter { display: inline-flex; align-items: center; gap: 2px; margin-right: .2rem; }
.diff-meter i { width: 9px; height: 5px; border-radius: 1px; background: var(--line); }
.diff-meter i.on { background: var(--accent); }
.proj-layout { max-width: 1060px; margin: 0 auto; padding: 1.6rem 16px 3rem; display: grid; grid-template-columns: minmax(0, 1fr) 270px; gap: 3rem; align-items: start; }
.proj-layout .lesson { max-width: none; }
.spec-card { position: sticky; top: 76px; padding: 1rem 1.1rem; background: var(--surface2); border-radius: var(--radius); }
.spec-card h4 { margin: 0 0 .4rem; font-size: 1rem; }
.spec-card dl { margin: 0 0 .8rem; }
.spec-card dl div { display: flex; justify-content: space-between; gap: 1rem; padding: .4rem 0; border-bottom: 1px solid var(--line); font-size: .93rem; }
.spec-card dt { color: var(--muted); }
.spec-card dd { margin: 0; font-weight: 600; text-align: right; }
.spec-card .learn ul { margin: .3rem 0 0; padding-left: 1.1rem; font-size: .93rem; }
.parts-list { list-style: none; padding: 0; margin: .6rem 0 1rem; }
.parts-list label { display: flex; gap: .6rem; align-items: center; padding: .4rem 0; border-bottom: 1px solid var(--line); cursor: pointer; }
.parts-list input { accent-color: var(--good); }
.parts-list label:has(input:checked) { color: var(--muted); text-decoration: line-through; }
.no-code { padding: .9rem 1.1rem; background: var(--surface2); border-radius: var(--radius); color: var(--muted); }
.result-box { margin: 1.2rem 0; padding: .9rem 1.1rem; background: var(--good-soft); border-radius: var(--radius); }
.result-box .eyebrow { color: var(--good); }
.result-box p { margin: .2rem 0 0; }
.fixes { margin: 0; }
.fixes > div { padding: .65rem 0; border-bottom: 1px solid var(--line); }
.fixes dt { font-weight: 600; }
.fixes dd { margin: .15rem 0 0; color: var(--muted); }
.read-first { list-style: none; padding: 0 !important; }
.read-first a { display: flex; gap: .45rem; align-items: flex-start; padding: .2rem 0; font-size: .9rem; }
.challenge { margin-top: 2rem; padding: 1rem 1.2rem; background: var(--accent-soft); border-radius: var(--radius); }
.challenge .eyebrow { color: var(--accent-strong); }
.challenge p { margin: .3rem 0 0; }

/* ============ Glossary & certificate ============ */
.search { margin-top: .8rem; font-size: 1.02rem; padding: .7rem .9rem; }
.glossary { padding: 0 16px 3rem; }
.g-item { padding: .7rem 0; border-bottom: 1px solid var(--line); display: grid; grid-template-columns: 170px 1fr; gap: 1rem; }
.g-item dt { font-weight: 600; }
.g-item dd { margin: 0; color: var(--muted); }
.cert-form { display: flex; gap: .8rem; align-items: flex-end; padding: 0 16px; flex-wrap: wrap; }
.cert-form .ctl { flex: 1; min-width: 220px; margin: 0; }
.cert-view { padding: 1.4rem 16px; }
.cert-view canvas { width: 100%; height: auto; border-radius: 6px; box-shadow: 0 4px 20px rgba(0,0,0,.12); }
.locked { padding: 0 16px; }
.locked h2 { margin-top: .5rem; }
.unlock { list-style: none; padding: 0; margin: 1rem 0 1.5rem; }
.unlock li { display: flex; gap: .6rem; align-items: center; padding: .5rem 0; border-bottom: 1px solid var(--line); }
.unlock small { margin-left: auto; color: var(--muted); }
.verify { margin: 2.5rem 16px 3rem; padding: 1.2rem 1.3rem; background: var(--surface2); border-radius: var(--radius); }
.verify h3 { margin-top: 0; }
.vres { margin-left: .6rem; font-weight: 600; }
.vres.ok { color: var(--good); }
.vres.bad { color: var(--bad); }

.share-box { margin-top: 1.6rem; padding: 1.2rem 1.3rem; background: var(--surface2); border-radius: var(--radius); }
.share-box h3 { margin: 0 0 .8rem; }
.share-box textarea { width: 100%; margin: .4rem 0 .6rem; padding: .7rem .8rem; border: 1px solid var(--line); border-radius: 6px; background: var(--bg); color: var(--fg); font: .92rem/1.5 var(--font); resize: vertical; }
.share-box .copy-txt { font-size: .88rem; padding: .32rem .7rem; }
.f-share { display: flex; flex-wrap: wrap; gap: .4rem 1rem; margin-top: 1rem; font-size: .92rem; }
.f-share span { color: var(--muted); }

/* ============ Footer ============ */
.footer { margin-top: 4rem; border-top: 1px solid var(--line); background: var(--surface2); }
.footer-inner { max-width: 980px; margin: 0 auto; padding: 2.4rem 16px 1.6rem; display: grid; grid-template-columns: 1fr 1.4fr .5fr; gap: 2rem 2.5rem; }
.f-title { font: 600 1.05rem var(--head); margin: 0 0 .5rem; color: var(--fg); }
.footer p { color: var(--muted); font-size: .96rem; }
.about .role { margin: -.2rem 0 .6rem; font-size: .92rem; color: var(--fg); }
.contact ul { list-style: none; padding: 0; margin: .9rem 0 0; }
.contact li { display: flex; align-items: center; gap: .5rem; padding: .3rem 0; flex-wrap: wrap; font-size: .96rem; }
.contact li > span:first-child { width: 5.4rem; color: var(--muted); font-size: .88rem; }
.contact a { color: var(--fg); font-weight: 600; }
.copy-txt { border: 1px solid var(--line); background: var(--surface); color: var(--muted); border-radius: 4px; font: 500 .74rem var(--font); padding: .08rem .45rem; cursor: pointer; }
.copy-txt:hover { color: var(--fg); }
.btn.linkedin { background: #0a66c2; color: #fff; }
.btn.linkedin:hover { background: #084f96; }
.btn.linkedin svg { width: 16px; height: 16px; }
.f-links { display: flex; flex-direction: column; gap: .25rem; font-size: .96rem; }
.f-links a { color: var(--muted); }
.f-links a:hover { color: var(--fg); }
.f-bottom { max-width: 980px; margin: 0 auto; padding: 1rem 16px 1.6rem; border-top: 1px solid var(--line); color: var(--muted); font-size: .88rem; }

.confetti { position: fixed; inset: 0; pointer-events: none; z-index: 100; overflow: hidden; }
.confetti i { position: absolute; top: -12px; width: 7px; height: 12px; border-radius: 2px; animation: fall linear forwards; }
@keyframes fall { to { transform: translateY(105vh) rotate(720deg); opacity: .7; } }

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

/* ============ Responsive ============ */
@media (max-width: 1060px) {
  .search-wrap { width: 200px; }
  .search-wrap kbd { display: none; }
  .nav a { padding: .35rem .5rem; }
}
@media (max-width: 1140px) {
  .lesson-layout { grid-template-columns: 220px minmax(0, 1fr); gap: 2.4rem; }
  .toc { display: none; }
}
@media (max-width: 900px) {
  .lesson-layout { grid-template-columns: 1fr; gap: 1rem; }
  .side { position: fixed; top: 0; left: 0; bottom: 0; width: min(320px, 86vw); max-height: none; z-index: 90; background: var(--bg); padding: calc(env(safe-area-inset-top, 0px) + 1rem) 1rem 1rem; overflow: auto; transform: translateX(-105%); transition: transform .2s; box-shadow: 4px 0 24px rgba(0,0,0,.18); }
  .map-open .side { transform: none; }
  .map-open .map-scrim { display: block; position: fixed; inset: 0; background: rgba(0,0,0,.35); z-index: 80; }
  .side-close, .map-btn { display: inline-flex; }
  .map-btn { margin-bottom: .6rem; }
  .start-steps { grid-template-columns: 1fr; }
  .modules { grid-template-columns: 1fr; }
  .w-grid.four { grid-template-columns: 1fr 1fr; }
  .proj-layout { grid-template-columns: 1fr; gap: 1.5rem; }
  .proj-layout .spec-card { position: static; order: -1; }
  .footer-inner { grid-template-columns: 1fr 1fr; }
  .about { grid-column: 1 / -1; }
  .feature-projects, .how { grid-template-columns: 1fr 1fr; }
  .cat-grid { grid-template-columns: 1fr 1fr; }
  .track-row { grid-template-columns: 1fr; }
}
@media (max-width: 680px) {
  body { font-size: 16.5px; }
  .menu-btn, .search-btn { display: grid; }
  .search-wrap { display: none; position: fixed; top: calc(56px + env(safe-area-inset-top, 0px)); left: 0; right: 0; width: auto; margin: 0; padding: .6rem 16px; background: var(--bg); border-bottom: 1px solid var(--line); z-index: 60; }
  .search-open .search-wrap { display: flex; }
  .search-wrap .s-ico { left: calc(16px + .65rem); }
  .search-wrap kbd { display: none; }
  .q-res { left: 16px; right: 16px; width: auto; }
  .pager { grid-template-columns: 1fr; }
  .interview { columns: 1; }
  .nav { position: fixed; top: calc(56px + env(safe-area-inset-top, 0px)); left: 0; right: 0; flex-direction: column; background: var(--bg); border-bottom: 1px solid var(--line); padding: .5rem 16px 1rem; display: none; }
  .nav-open .nav { display: flex; }
  .top-actions { margin-left: auto; }
  .mod-list a { grid-template-columns: 2rem 1fr; }
  .mod-list .s { grid-column: 2; grid-row: auto; }
  .feature-projects, .how { grid-template-columns: 1fr; }
  .branch-grid, .cat-grid, .industry, .path-lessons { grid-template-columns: 1fr; }
  .uses { columns: 1; }
  .track-mods .lvl { display: none; }
  .track-head { grid-template-columns: 1.8rem 1fr; }
  .footer-inner { grid-template-columns: 1fr; }
  .trio, .compare, .w-grid, .w-grid.three { grid-template-columns: 1fr; }
  .colorcode { grid-template-columns: repeat(2, 1fr); }
  .gate-stage, .cmos-wrap { grid-template-columns: 1fr; justify-items: center; }
  .gate-inputs { flex-direction: row; }
  .bits { gap: 3px; }
  .bit { font-size: 1.05rem; padding: .4rem 0; }
  .g-item { grid-template-columns: 1fr; gap: .1rem; }
  .lesson-nav .btn { width: 100%; }
  .reg-row { flex-direction: column; align-items: stretch; }
  .m-hero { flex-direction: column; align-items: flex-start; }
  .filter-row > span { width: 100%; }
}

@media print {
  .topbar, .footer, .cert-form, .verify, .btn-row, .page-head, .readbar { display: none !important; }
  body { background: #fff; }
  .cert-view { padding: 0; }
  .cert-view canvas { box-shadow: none; }
}