*{box-sizing:border-box}
body{font-family:system-ui,-apple-system,Segoe UI,Roboto,Helvetica,Arial,sans-serif;background:#f0f2f5;color:#111;margin:0;padding:24px}
.app{background:#fff;max-width:720px;margin:40px auto;padding:28px 24px;border-radius:14px;box-shadow:0 8px 30px rgba(0,0,0,.08)}
h1{margin:0 0 16px;font-size:28px}
.quiz h2{margin:0 0 12px;font-weight:600}
#answer-buttons{margin-top:6px}
.btn{display:block;width:100%;text-align:left;margin:10px 0;padding:12px 14px;border:1px solid #e5e7eb;border-radius:10px;background:#fff;cursor:pointer;font-size:16px}
.btn:hover:not([disabled]){background:#fafafa}
.btn:disabled{cursor:not-allowed;opacity:.9}
.correct{background:#d4edda;border-color:#badbcc}
.incorrect{background:#f8d7da;border-color:#f5c2c7}
#next-btn{display:none;margin-top:12px;padding:12px 18px;border:none;border-radius:10px;background:#111;color:#fff;font-size:16px;cursor:pointer}
#next-btn:hover{opacity:.9}
small{color:#374151}