:root{color-scheme:dark;--bg:#090f19;--surface:#121d2c;--line:#29384b;--ink:#e3eaf5;--muted:#9cacc2;--lav:#b7b5eb;--mint:#91d3c5}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--ink);font:16px/1.55 -apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif}button,a,input{touch-action:manipulation}button,a{ -webkit-tap-highlight-color:transparent}a{color:inherit}button{font:inherit;color:inherit;background:#1c2b40;border:1px solid var(--line);border-radius:12px;padding:12px 16px;cursor:pointer}button:focus-visible,a:focus-visible,input:focus-visible{outline:3px solid var(--mint);outline-offset:3px}button:disabled{opacity:.45;cursor:default}header{max-width:760px;margin:auto;padding:calc(18px + env(safe-area-inset-top)) 22px 16px;display:flex;justify-content:space-between;align-items:center}.brand{display:flex;gap:12px;text-decoration:none;font-size:22px;font-weight:650;line-height:1.2}.brand small{display:block;color:var(--muted);font-size:11px;letter-spacing:1.2px;margin-top:6px;font-weight:400}.mark{display:grid;place-items:center;border:1px solid #52647f;border-radius:12px;width:44px;color:#c7d8f3;background:#17263c;font-size:27px}.icon{padding:7px 13px;background:transparent;font-size:23px}main{max-width:760px;margin:auto;padding:12px 20px calc(112px + env(safe-area-inset-bottom))}h1{font-size:30px;line-height:1.18;letter-spacing:-.7px;margin:10px 0 14px}h2{font-size:21px;line-height:1.3;margin:0 0 15px}h3{font-size:17px;margin:0 0 8px}p{margin:0 0 16px}.muted{color:var(--muted);font-size:14px}.row{display:flex;align-items:center;justify-content:space-between;gap:12px}.stage{overflow:hidden;border:1px solid #334359;border-radius:26px;background:radial-gradient(ellipse at 50% 40%,#203654 0%,#0d1726 65%);position:relative;margin-bottom:22px}.stage-label{position:absolute;top:18px;left:20px;color:#becde2;font-size:12px;z-index:1}.viewer{height:285px;position:relative;touch-action:pan-y}.viewer canvas{display:block;width:100%;height:100%}.stage-controls{position:absolute;right:14px;top:12px;z-index:2}.stage-controls button{font-size:12px;padding:7px 10px;background:#122037d9}.stage-caption{text-align:center;padding:0 20px 20px}.stage-caption strong{display:block;font-size:24px;letter-spacing:2px}.stage-caption small{color:var(--muted)}.primary{background:var(--lav);border-color:var(--lav);color:#14192b;font-weight:650;display:block;width:100%;text-align:center;text-decoration:none;border-radius:13px;padding:14px 18px}.secondary{display:block;text-align:center;text-decoration:none;border:1px solid #465777;padding:12px;border-radius:12px;margin-top:12px}.progress-card{padding:20px;background:var(--surface);border:1px solid var(--line);border-radius:18px;margin-bottom:22px}progress{width:100%;height:7px;border:0;border-radius:10px;overflow:hidden;margin:10px 0 16px;appearance:none}progress::-webkit-progress-bar{background:#29364b}progress::-webkit-progress-value{background:var(--mint)}progress::-moz-progress-bar{background:var(--mint)}.section-head{margin:30px 0 16px}.lesson-link{display:flex;gap:15px;align-items:center;padding:18px 0;text-decoration:none;border-bottom:1px solid var(--line)}.lesson-link .num{display:grid;place-items:center;flex-shrink:0;width:42px;height:42px;border-radius:12px;background:#1a2b42;color:#acc8ef;font-size:17px}.lesson-link.done .num{background:#1c3935;color:var(--mint)}.lesson-link strong{display:block;font-size:16px;font-weight:550}.lesson-link small{display:block;color:var(--muted);font-size:12px;margin-top:4px}.lesson-link .chevron{margin-left:auto;color:#71839d}.tabs{display:flex;gap:8px;margin:18px 0}.tabs button{flex:1;font-size:14px;padding:10px 5px}.tabs .selected{background:#323454;border-color:#9b98cc}.note{padding:16px 18px;border-left:3px solid var(--lav);background:#1a2033;border-radius:0 10px 10px 0;font-size:14px;margin:18px 0}.lesson-video{width:100%;display:block;aspect-ratio:16/9;border-radius:14px;background:#000;margin:18px 0}ol{padding-left:22px}li{margin:0 0 16px;padding-left:5px}.quiz{border:1px solid #43516a;border-radius:18px;padding:20px;background:#141f30;margin-top:28px}.option{display:block;width:100%;text-align:left;margin:10px 0;background:#1c2a3f;line-height:1.4}.option.wrong{border-color:#e79d9e;background:#40252e}.option.correct{border-color:var(--mint);background:#1d3a35}.feedback{padding:13px 0 0;color:var(--muted)}.feedback.good{color:var(--mint)}.feedback.bad{color:#f3b3b7}.practice{margin:24px 0}.practice label{display:flex;gap:12px;align-items:flex-start;padding:16px;background:#172b2c;border-radius:13px}.practice input{width:23px;height:23px;flex-shrink:0;accent-color:var(--mint)}.back{display:inline-block;color:var(--muted);font-size:14px;text-decoration:none;margin-bottom:10px}.nav-next{margin:24px 0}.resources a{display:block;margin:12px 0;background:#162338;border:1px solid var(--line);padding:16px;border-radius:13px;text-decoration:none}.resources a small{color:var(--muted);display:block;font-size:12px;margin-top:3px}details{border-top:1px solid var(--line);margin-top:24px;padding-top:18px}summary{cursor:pointer;font-weight:550}details p{font-size:14px;color:var(--muted);margin-top:14px}nav{position:fixed;bottom:0;left:50%;transform:translateX(-50%);width:100%;max-width:760px;display:flex;padding:10px 12px calc(10px + env(safe-area-inset-bottom));background:#0e1726f2;backdrop-filter:blur(20px);border-top:1px solid var(--line);z-index:10}nav a{text-decoration:none;flex:1;text-align:center;color:#8294ae;font-size:22px;padding:4px;border-radius:12px}nav span{display:block;font-size:11px;line-height:1.4}nav a.active{background:#25304a;color:#d0ccf7}dialog{background:#142033;color:var(--ink);border:1px solid #41536c;border-radius:22px;padding:24px;width:calc(100% - 32px);max-width:440px}dialog::backdrop{background:#000a}.toggle{display:flex;justify-content:space-between;padding:16px 0;border-bottom:1px solid var(--line)}.toggle input{width:24px;height:24px;accent-color:var(--lav)}dialog .muted{margin-top:18px}#toast{position:fixed;bottom:100px;left:50%;transform:translateX(-50%);max-width:90%;background:#293c54;border-radius:12px;padding:12px 18px;z-index:30;display:none}.loading{padding:40px;text-align:center}.fallback-device{margin:35px auto;width:210px;height:160px;border:12px solid #718398;border-radius:16px;background:#112c29;color:var(--mint);display:grid;place-items:center;font-size:24px;box-shadow:15px 15px 0 #283548}.badge{color:var(--mint);font-size:13px}.copy{font-size:13px}.complete{text-align:center;padding:26px;border:1px solid #3b6e63;background:#142c2c;border-radius:18px}.complete strong{font-size:26px;display:block;margin-bottom:12px}@media(min-width:600px){.viewer{height:350px}h1{font-size:36px}main{padding-top:24px}.stage{max-width:520px;margin:0 auto 25px}}@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important}}

/* Keep native hidden semantics above component display rules. */
[hidden]{display:none!important}