:root{--bg:#0f172a;--surface:#1e293b;--text:#e2e8f0;--muted:#94a3b8;--accent:#38bdf8;--correct:#22c55e;--wrong:#ef4444}*{box-sizing:border-box}body,html{margin:0;padding:0;background:var(--bg);color:var(--text);font-family:system-ui,-apple-system,Segoe UI,Hiragino Sans,Noto Sans JP,sans-serif;-webkit-font-smoothing:antialiased}main{max-width:720px;margin:0 auto;padding:24px 16px 64px}a{color:var(--accent)}.card{background:var(--surface);border-radius:16px;padding:20px;margin:16px 0}.meta-row{display:flex;gap:8px;align-items:center;flex-wrap:wrap;margin-bottom:12px;font-size:13px;color:var(--muted)}.badge{display:inline-block;padding:2px 10px;border-radius:999px;background:rgba(56,189,248,.15);color:var(--accent);font-size:12px}.question-body{font-size:18px;line-height:1.7;margin:8px 0 20px}.choices{display:flex;flex-direction:column;gap:10px}.choice{text-align:left;padding:14px 16px;border-radius:12px;border:1px solid #334155;background:#0b1220;color:var(--text);font-size:16px;cursor:pointer;transition:border-color .15s,background .15s}.choice:hover:enabled{border-color:var(--accent)}.choice.correct{border-color:var(--correct);background:rgba(34,197,94,.15)}.choice.wrong{border-color:var(--wrong);background:rgba(239,68,68,.15)}.choice:disabled{cursor:default}.explanation{margin-top:18px;padding:16px;border-radius:12px;background:#0b1220;border-left:3px solid var(--accent);line-height:1.7}.explanation svg{max-width:100%;height:auto;margin:12px 0}.primary-btn{margin-top:18px;width:100%;padding:14px;border:none;border-radius:12px;background:var(--accent);color:#06283d;font-size:16px;font-weight:700;cursor:pointer}.streak{font-weight:700;color:var(--correct)}.ad-placeholder{margin:16px 0;padding:24px;text-align:center;font-size:12px;color:var(--muted);border:1px dashed #334155;border-radius:12px}