:root{color-scheme:light dark;--bg:#fbfaf7;--fg:#1c1a17;--dim:#6b665e;--line:#ddd8cf;--card:#fff;--accent:#2563eb;--right:#15803d;--right-bg:#dcfce7;--wrong:#b91c1c;--wrong-bg:#fee2e2}@media (prefers-color-scheme:dark){:root{--bg:#171614;--fg:#f0ede8;--dim:#9c968c;--line:#35322d;--card:#211f1c;--accent:#60a5fa;--right:#4ade80;--right-bg:#14321f;--wrong:#f87171;--wrong-bg:#3a1a1a}}*{box-sizing:border-box;-webkit-tap-highlight-color:transparent}body,html{margin:0;padding:0;background:var(--bg);color:var(--fg);font:18px/1.7 system-ui,-apple-system,PingFang SC,Noto Sans SC,sans-serif}main{max-width:720px;margin:0 auto;padding:1.25rem 1rem 5rem}h1{font-size:1.5rem;margin:0 0 .25rem}h2{font-size:1.125rem;margin:2rem 0 .75rem}p{margin:.5rem 0}a{color:var(--accent)}.sub{font-size:.95rem;margin-bottom:1.5rem}.dim,.sub{color:var(--dim)}.card{border:1px solid var(--line);border-radius:14px;padding:1.25rem;margin-bottom:1rem}.card,.tap{background:var(--card)}.tap{display:block;width:100%;min-height:48px;text-align:left;font:inherit;color:inherit;border:2px solid var(--line);border-radius:12px;padding:.85rem 1rem;margin-bottom:.6rem;cursor:pointer;transition:border-color .12s,background .12s}.tap:hover:not(:disabled){border-color:var(--accent)}.tap:disabled{cursor:default}.tap.right{border-color:var(--right);background:var(--right-bg)}.tap.wrong{border-color:var(--wrong);background:var(--wrong-bg)}.mark{font-weight:700;margin-right:.5rem}.btn{font:inherit;min-height:48px;padding:.7rem 1.5rem;border-radius:12px;border:2px solid var(--line);background:var(--card);color:inherit;cursor:pointer}.btn.primary{background:var(--accent);color:#fff;border-color:var(--accent)}.btn:disabled{opacity:.5;cursor:default}.row{display:flex;gap:.75rem;flex-wrap:wrap;align-items:center}.stem{font-size:1.2rem;font-weight:600;line-height:1.6;margin-bottom:1.25rem}.explain{margin-top:1.25rem;padding-top:1.25rem;border-top:1px solid var(--line);white-space:pre-wrap}.tag{display:inline-block;font-size:.8rem;border:1px solid var(--line);border-radius:999px;padding:.1rem .6rem;margin:0 .35rem .35rem 0}.progress,.tag{color:var(--dim)}.progress{font-size:.9rem;margin-bottom:1rem}.stars{display:flex;gap:.25rem}.star{font-size:1.6rem;line-height:1;background:none;border:none;cursor:pointer;padding:.2rem;color:var(--dim)}.star.on{color:#f59e0b}.subject-row{display:flex;justify-content:space-between;align-items:center;gap:1rem}