:root{--bg:#f4f7fb;--surface:#fff;--ink:#172238;--muted:#60708a;--line:#d9e2ef;--primary:#0d7b73;--primary2:#e8743b;--soft:#e6f6f3;--good:#087f5b;--bad:#c23535;--shadow:0 16px 42px rgba(37,55,91,.1)}[data-theme=dark]{--bg:#111827;--surface:#1c2637;--ink:#eef4ff;--muted:#aebbd0;--line:#35445b;--primary:#54d6c8;--primary2:#ff9c69;--soft:#203c3b;--good:#5ee6b3;--bad:#ff8b8b;--shadow:0 16px 42px rgba(0,0,0,.25)}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--ink);font:16px/1.55 system-ui,-apple-system,"Segoe UI",sans-serif}.site-header{background:linear-gradient(115deg,#075f68,#166b50);color:white}.header-inner{max-width:1160px;margin:auto;padding:24px;display:flex;justify-content:space-between;align-items:center}.header-inner h1,.header-inner p{margin:0}.header-inner p{opacity:.82}.icon-btn{width:42px;height:42px;border:1px solid #ffffff55;border-radius:50%;color:white;background:#ffffff18;font-size:20px}.section-nav{display:flex;justify-content:center;gap:8px;padding:12px;position:sticky;top:0;z-index:5;background:color-mix(in srgb,var(--surface) 94%,transparent);border-bottom:1px solid var(--line)}.nav-btn,.btn{border:1px solid var(--line);border-radius:12px;padding:10px 15px;background:var(--surface);color:var(--ink);font-weight:750;cursor:pointer}.nav-btn.active,.btn.primary{background:var(--primary);border-color:var(--primary);color:white}.btn.danger{color:var(--bad)}main{width:min(1120px,calc(100% - 28px));margin:28px auto 60px}.content-section{display:none}.content-section.active{display:block}.hero{display:grid;grid-template-columns:1.4fr .8fr;gap:24px;align-items:center;background:linear-gradient(135deg,var(--surface),var(--soft));padding:32px;border:1px solid var(--line);border-radius:24px;box-shadow:var(--shadow)}h2{margin:.25rem 0 1rem;font-size:clamp(1.7rem,3vw,2.55rem);line-height:1.1}.eyebrow{color:var(--primary);font-size:.8rem;font-weight:900;text-transform:uppercase;letter-spacing:.12em}.formula{text-align:center;font-size:2rem;font-weight:900;color:var(--primary);padding:30px;border-radius:20px;background:var(--surface);border:1px solid var(--line)}.formula span{font-size:1rem;color:var(--muted)}.cards,.task-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:16px;margin:22px 0}.cards article,.panel,.task-card{background:var(--surface);border:1px solid var(--line);border-radius:18px;padding:22px;box-shadow:var(--shadow)}.cards h3,.task-card h3{margin-top:0}.section-title{display:flex;justify-content:space-between;align-items:end;gap:12px;margin-bottom:18px}.badge{padding:8px 12px;border-radius:99px;background:var(--soft);color:var(--primary);font-weight:850}.lab-grid{display:grid;grid-template-columns:360px 1fr;gap:18px}.controls{display:grid;gap:18px}.controls label{display:grid;gap:6px;font-weight:650}input[type=range]{width:100%;accent-color:var(--primary)}input[type=number],select,.task-answer{width:100%;padding:10px;border-radius:10px;border:1px solid var(--line);background:var(--bg);color:var(--ink)}.force-line{height:210px;display:flex;align-items:center;justify-content:center;gap:25px;border-bottom:5px solid var(--line);background:linear-gradient(var(--soft),transparent);border-radius:14px}.block{width:100px;padding:28px 8px;text-align:center;border-radius:15px;background:var(--primary);color:white;font-weight:900}.force{font-size:1.35rem;font-weight:900;color:var(--primary2)}.meters{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin-top:16px}.meters div{padding:11px;background:var(--bg);border-radius:12px}.meters span{display:block;color:var(--muted);font-size:.8rem}.feedback,.task-feedback,.solution{margin-top:14px;padding:12px;border-radius:12px;background:var(--bg)}.task-grid{grid-template-columns:repeat(2,1fr)}.task-card.completed{border-color:var(--good)}.task-meta{display:flex;justify-content:space-between;color:var(--muted);font-size:.8rem}.answer-row{display:grid;grid-template-columns:1fr auto;gap:8px}.hint-btn{border:0;background:none;color:var(--primary);font-weight:750;padding:10px 0;cursor:pointer}.hint{border-left:4px solid var(--primary);padding:9px 12px;background:var(--soft)}.task-feedback.success{color:var(--good);background:color-mix(in srgb,var(--good) 12%,var(--surface))}.task-feedback.error{color:var(--bad);background:color-mix(in srgb,var(--bad) 10%,var(--surface))}footer{text-align:center;padding:24px;color:var(--muted);border-top:1px solid var(--line);background:var(--surface)}@media(max-width:800px){.hero,.lab-grid{grid-template-columns:1fr}.cards{grid-template-columns:1fr}.task-grid{grid-template-columns:1fr}.section-nav{justify-content:flex-start;overflow:auto}.nav-btn{white-space:nowrap}}@media(max-width:520px){.meters{grid-template-columns:1fr}.section-title{align-items:start;flex-direction:column}.answer-row{grid-template-columns:1fr}.force-line{gap:8px}.force{font-size:1rem}}