:root{color-scheme:light;--bg:#f3f5f0;--paper:#fff;--ink:#18342f;--muted:#47635c;--accent:#17634e;--line:#c8d7cb;--soft:#e7f1e9}*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:1rem}[data-theme="dark"]{color-scheme:dark;--bg:#101f1b;--paper:#192e27;--ink:#ecf4ed;--muted:#bdd2c5;--accent:#95e6bc;--line:#466456;--soft:#213f32}body{margin:0;background:var(--bg);color:var(--ink);font:1rem/1.7 system-ui,sans-serif}header,main,footer{max-width:1120px;margin:auto;padding:2rem}header{padding-top:1.5rem}.tools{float:right;display:flex;gap:.5rem}h1{font-size:clamp(3rem,8vw,6rem);line-height:1.05;letter-spacing:-.055em;margin:2rem 0 1rem}h1 span{color:var(--accent)}h2{font-size:clamp(1.6rem,4vw,2.4rem);line-height:1.2;letter-spacing:-.025em}h3{line-height:1.3}.lead{font-size:1.3rem;max-width:700px}.eyebrow{text-transform:uppercase;letter-spacing:.12em;font-size:.8rem;font-weight:750;color:var(--accent)}section{background:var(--paper);border:1px solid var(--line);border-radius:20px;padding:2rem;margin-bottom:1.5rem;min-width:0}nav{display:grid;grid-template-columns:1fr 1fr;gap:.6rem;margin-top:1.5rem}a{color:var(--accent)}nav a{padding:.7rem;background:var(--soft);border-radius:8px;text-decoration:none;font-weight:650}button{font:inherit;font-weight:650;padding:.5rem .9rem;border:1px solid var(--line);border-radius:8px;background:var(--soft);color:var(--ink);cursor:pointer}button:hover,nav a:hover{outline:2px solid var(--accent)}button:focus-visible,input:focus-visible,select:focus-visible,summary:focus-visible,a:focus-visible{outline:3px solid var(--accent);outline-offset:3px}.lesson-grid{display:grid;grid-template-columns:1.2fr 1fr;gap:1.5rem}.lesson-grid>*{min-width:0}aside{background:var(--soft);padding:1rem 1.3rem;border-radius:12px}li{margin:.65rem 0}.sessions{font-size:.95rem;color:var(--muted)}.challenge{border-left:4px solid var(--accent);padding:1rem;background:var(--soft);border-radius:0 12px 12px 0}.challenge label{display:block;margin-bottom:.6rem}input:not([type="range"]),select{font:inherit;padding:.7rem;background:var(--paper);color:var(--ink);border:1px solid var(--line);border-radius:8px;max-width:100%;margin-bottom:.6rem}.challenge button{margin:.3rem}input[type="range"]{display:block;width:100%;accent-color:var(--accent)}.feedback{min-height:1.7em;font-weight:650}[data-correct="false"] .feedback{color:var(--ink)}details{border-top:1px solid var(--line);margin-top:1.4rem;padding-top:1rem}summary{cursor:pointer;font-weight:700}.lab-controls{display:grid;grid-template-columns:1fr 1fr;gap:1.5rem}.lab-controls label{display:block}.lab-controls select{display:block;width:100%}.lab-controls output{font-weight:750}.readings{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:.7rem}.readings>div{background:var(--soft);padding:1rem;border-radius:10px}.readings>div>span,.readings>div>strong{display:block}.readings>div>span{font-size:.85rem;color:var(--muted)}.readings>div>strong{font-size:1.2rem}.table-wrap{overflow-x:auto}table{width:100%;border-collapse:collapse}td,th{text-align:left;padding:.8rem;border-bottom:1px solid var(--line)}footer{color:var(--muted)}.katex-display{max-width:100%}
.formula-strip{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:.8rem;margin:1.4rem 0}.formula-strip>div{background:var(--soft);border:1px solid var(--line);border-radius:12px;padding:.85rem 1rem;min-width:0}.formula-strip>div>span{display:block;font-size:.85rem;font-weight:700;color:var(--muted)}.scoreboard-box{background:var(--soft);border:1px solid var(--line);border-radius:14px;padding:1rem 1.2rem;margin:1.2rem 0}.scoreboard-head{display:flex;justify-content:space-between;align-items:center;gap:1rem;flex-wrap:wrap}.scoreboard-head h3,.scoreboard-head p{margin:.15rem 0}.progress-track{height:12px;background:var(--paper);border:1px solid var(--line);border-radius:999px;overflow:hidden;margin-top:.6rem}.progress-fill{height:100%;width:0%;background:var(--accent);transition:width .25s ease}.exercises-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:1.2rem;margin-top:1.2rem}.interactive-exercise{background:var(--soft);border:1px solid var(--line);border-left:4px solid var(--accent);border-radius:12px;padding:1.2rem;min-width:0;display:flex;flex-direction:column}.interactive-exercise h3{margin:.2rem 0 .5rem}.exercise-step{background:var(--paper);border:1px solid var(--line);border-radius:10px;padding:.85rem;margin-bottom:.75rem}.exercise-step label{display:block;font-weight:650;margin-bottom:.45rem;font-size:.95rem}.exercise-step input,.exercise-step select{width:100%;margin-bottom:.25rem}.step-feedback{margin:.25rem 0 0;min-height:1.4em;font-size:.92rem;font-weight:650}.step-feedback[data-ok="true"]{color:var(--accent)}.exercise-actions{display:flex;gap:.5rem;flex-wrap:wrap;margin-top:.2rem}.exercise-summary{font-weight:700;min-height:1.5em;margin:.5rem 0 0}.circuit-figure{margin:1.2rem 0;background:var(--soft);border:1px solid var(--line);border-radius:14px;padding:1rem}.circuit-figure figcaption{font-size:.88rem;color:var(--muted);margin-top:.4rem;text-align:center}.circuit-svg{width:100%;height:auto;display:block;max-height:240px}.svg-board{fill:var(--paper);stroke:var(--line);stroke-width:1.5}.wire-active{stroke:var(--accent)}.wire-idle,.wire-open{stroke:var(--muted);stroke-dasharray:6 4}.svg-node,.svg-source{fill:var(--ink);stroke:var(--ink)}.svg-resistor{fill:var(--soft);stroke:var(--accent);stroke-width:2}.svg-meter{fill:var(--paper);stroke:var(--accent);stroke-width:2.5}.svg-meter-text{fill:var(--accent);font-weight:800;font-size:14px}.svg-label{fill:var(--muted);font-size:12px;font-weight:650}.svg-label-strong{fill:var(--ink);font-size:13px;font-weight:750}.svg-sub{fill:var(--accent);font-size:12px;font-weight:700}.lab-mission{margin-top:1.2rem;padding:1rem 1.2rem;background:var(--soft);border-left:4px solid var(--accent);border-radius:0 12px 12px 0}
@media(max-width:820px){.exercises-grid,.formula-strip{grid-template-columns:1fr}}
@media(max-width:650px){header,main,footer{padding:1rem}header{padding-top:1rem}.tools{float:none;margin:1rem 0;flex-wrap:wrap}section{padding:1.1rem;border-radius:12px}.lesson-grid,nav,.lab-controls,.readings,.exercises-grid,.formula-strip{grid-template-columns:1fr}.challenge input,.challenge select{width:100%}h1{margin-top:1.5rem}}@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}.progress-fill{transition:none}}@media print{:root,[data-theme="dark"]{color-scheme:light;--bg:#fff;--paper:#fff;--ink:#000;--muted:#222;--accent:#000;--line:#aaa;--soft:#f5f5f5}body{font-size:10pt}header,main,footer{max-width:none;padding:0}h1{font-size:32pt}section{border:0;padding:0;border-radius:0;margin:1rem 0;break-before:page}.intro{break-before:auto}.tools,button,nav,.lab-controls,.challenge input,.challenge select,.feedback,#progress,.scoreboard-box,.exercise-actions,.step-feedback,.exercise-summary{display:none}.lesson-grid,.exercises-grid,.formula-strip{display:block}.interactive-exercise,.exercise-step,aside,details,.circuit-figure{break-inside:avoid;margin-bottom:.8rem}.sessions{color:#222}a{color:#000}.readings{grid-template-columns:1fr 1fr}.katex{color:#000!important}}
@media print{.katex-display,[data-theme="dark"] .katex-display{background:#fff!important;color:#000!important;border-color:#bbb!important;border-left-color:#555!important}}
