:root{--course-accent:#06b6d4;--course-accent-2:#22d3ee;--course-deep:#0a0f14;--course-surface:#141c27;--course-border:rgba(255,255,255,.1);--course-muted:#94a3b8;--course-warm:#f59e0b}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--course-deep);color:#f1f5f9;font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif}
button,a{font:inherit}.course-header{position:sticky;top:0;z-index:50;display:flex;align-items:center;justify-content:space-between;gap:1rem;min-height:68px;padding:.75rem clamp(1rem,4vw,3rem);border-bottom:1px solid var(--course-border);background:rgba(10,15,20,.9);backdrop-filter:blur(16px)}
.brand{display:flex;align-items:center;gap:.65rem;color:#fff;text-decoration:none;font-weight:800}.brand img{width:38px;height:38px;object-fit:contain}.header-tools{display:flex;align-items:center;gap:1rem}.progress-wrap{display:flex;align-items:center;gap:.65rem;color:var(--course-muted);font-size:.78rem}.progress-track{display:block;width:120px;height:5px;overflow:hidden;border-radius:99px;background:#263241}.progress-track span{display:block;width:0;height:100%;background:var(--course-accent);transition:width .25s ease}
.language-switch{display:flex;padding:3px;border:1px solid var(--course-border);border-radius:9px}.language-switch button{border:0;border-radius:6px;padding:.34rem .55rem;background:transparent;color:var(--course-muted);cursor:pointer;font-size:.72rem;font-weight:800}.language-switch button.active{background:var(--course-accent);color:#061017}.exit-link{color:var(--course-muted);text-decoration:none;font-size:.85rem}.exit-link:hover{color:#fff}
.course-shell{display:grid;grid-template-columns:290px minmax(0,1fr);min-height:calc(100vh - 68px)}.course-nav{position:sticky;top:68px;height:calc(100vh - 68px);overflow:auto;padding:2rem 1.25rem;border-right:1px solid var(--course-border);background:rgba(20,28,39,.62)}.nav-intro>span,.lesson-kicker{color:var(--course-accent-2);font-size:.7rem;font-weight:900;letter-spacing:.14em;text-transform:uppercase}.nav-intro h1{margin:.4rem 0 0;font-family:Georgia,serif;font-size:1.6rem}.nav-intro p{margin:.45rem 0 1.5rem;color:var(--course-muted);font-size:.78rem;line-height:1.5}
#moduleNav{display:grid;gap:.55rem}.module-button{width:100%;display:grid;grid-template-columns:2rem 1fr auto;gap:.55rem;align-items:center;border:1px solid transparent;border-radius:12px;padding:.72rem;background:transparent;color:#cbd5e1;text-align:left;cursor:pointer}.module-button:hover{background:rgba(255,255,255,.04)}.module-button.active{border-color:rgba(6,182,212,.45);background:rgba(6,182,212,.08)}.module-number{font-family:ui-monospace,monospace;color:var(--course-accent);font-size:.72rem}.module-title{font-size:.82rem;font-weight:700;line-height:1.3}.module-count{font-size:.66rem;color:#64748b}
.lesson-stage{padding:clamp(1.25rem,4vw,4rem);min-width:0}.lesson-card{max-width:980px;min-height:560px;margin:0 auto;padding:clamp(1.4rem,4vw,3.5rem);border:1px solid var(--course-border);border-radius:24px;background:linear-gradient(145deg,rgba(20,28,39,.96),rgba(10,15,20,.98));box-shadow:0 24px 60px rgba(0,0,0,.2)}.lesson-meta{display:flex;align-items:center;justify-content:space-between;gap:1rem;color:#64748b;font-family:ui-monospace,monospace;font-size:.74rem}.lesson-card h2{max-width:800px;margin:1rem 0 .8rem;font-family:Georgia,serif;font-size:clamp(2rem,4vw,3.45rem);line-height:1.06}.lesson-lead{max-width:760px;margin:0 0 2rem;color:#cbd5e1;font-size:1.08rem;line-height:1.7}.lesson-body{display:grid;gap:1rem;color:#cbd5e1;line-height:1.7}.lesson-body p{margin:0}.lesson-body ul{margin:.2rem 0;padding-left:1.25rem}.lesson-body li+li{margin-top:.45rem}.formula{overflow:auto;border-left:3px solid var(--course-accent);border-radius:0 12px 12px 0;padding:1rem 1.2rem;background:rgba(0,0,0,.26);font-size:1.03rem}.engineering-note{border:1px solid rgba(245,158,11,.26);border-radius:14px;padding:1rem 1.1rem;background:rgba(245,158,11,.07);color:#fde68a}.comparison{width:100%;border-collapse:collapse;font-size:.9rem}.comparison th,.comparison td{padding:.72rem;border-bottom:1px solid var(--course-border);text-align:left}.comparison th{color:var(--course-accent-2)}
.lesson-actions{max-width:980px;margin:1rem auto 0;display:grid;grid-template-columns:1fr auto 1fr;gap:.75rem}.lesson-actions button{border:1px solid var(--course-border);border-radius:12px;padding:.8rem 1rem;background:var(--course-surface);color:#cbd5e1;cursor:pointer}.lesson-actions button:hover{border-color:rgba(6,182,212,.5);color:#fff}.lesson-actions button:disabled{opacity:.35;cursor:not-allowed}#completeLesson{background:var(--course-accent);color:#061017;font-weight:800}#completeLesson.completed{background:#166534;color:#dcfce7}#nextLesson{text-align:right}
.simulator{margin-top:1.8rem;border-top:1px solid var(--course-border);padding-top:2rem}.sim-heading{display:flex;align-items:flex-start;justify-content:space-between;gap:1rem;margin-bottom:1rem}.sim-heading h3{margin:.35rem 0 0;font-family:Georgia,serif;font-size:1.6rem}.preset{border:1px solid rgba(6,182,212,.4);border-radius:10px;padding:.65rem .8rem;background:rgba(6,182,212,.08);color:var(--course-accent-2);cursor:pointer}.sim-grid{display:grid;grid-template-columns:minmax(0,1.35fr) minmax(250px,.65fr);gap:1rem}.orbital-view{min-width:0}#orbitSvg{display:block;width:100%;height:auto;border:1px solid var(--course-border);border-radius:16px}.face-key{display:flex;flex-wrap:wrap;gap:1rem;margin-top:.65rem;color:var(--course-muted);font-size:.72rem}.face-key span:before{content:"";display:inline-block;width:22px;height:4px;margin-right:.45rem;vertical-align:middle}.active-key:before{background:#22d3ee}.back-key:before{border-top:2px dashed #64748b}.sim-controls{display:grid;align-content:start;gap:1rem;border:1px solid var(--course-border);border-radius:16px;padding:1rem;background:rgba(255,255,255,.025)}.sim-controls label{display:grid;grid-template-columns:1fr auto;gap:.3rem;color:#cbd5e1;font-size:.8rem}.sim-controls output{color:var(--course-accent-2);font-family:ui-monospace,monospace}.sim-controls input{grid-column:1/-1;width:100%;accent-color:var(--course-accent)}.metric-grid{display:grid;grid-template-columns:1fr 1fr;gap:.5rem}.metric-grid div{border-radius:10px;padding:.7rem;background:rgba(255,255,255,.04)}.metric-grid span{display:block;color:#64748b;font-size:.68rem}.metric-grid strong{display:block;margin-top:.2rem;color:#f8fafc;font-family:ui-monospace,monospace;font-size:.86rem}.sim-note{margin:0;color:#94a3b8;font-size:.72rem;line-height:1.5}
.metric-grid .status-metric{grid-column:1/-1;border:1px solid rgba(245,158,11,.18);background:rgba(245,158,11,.06)}
@media(max-width:900px){.course-shell{grid-template-columns:1fr}.course-nav{position:static;height:auto;border-right:0;border-bottom:1px solid var(--course-border);padding:1rem}.nav-intro p{margin-bottom:1rem}#moduleNav{display:flex;overflow:auto;padding-bottom:.3rem}.module-button{min-width:210px}.sim-grid{grid-template-columns:1fr}.progress-wrap{display:none}}
@media(max-width:620px){.course-header{align-items:flex-start}.brand span{display:none}.header-tools{gap:.45rem}.exit-link{display:none}.lesson-stage{padding:1rem}.lesson-card{min-height:0;border-radius:18px}.lesson-actions{grid-template-columns:1fr 1fr}#completeLesson{grid-column:1/-1;grid-row:1}#nextLesson{text-align:center}.sim-heading{display:grid}.metric-grid{grid-template-columns:1fr 1fr}}
@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important;transition:none!important}}