*{box-sizing:border-box}
body{margin:0;font-family:system-ui,-apple-system,"Segoe UI",Roboto,sans-serif;background:#f6f7f9;color:#1d232b;line-height:1.5;display:flex;flex-direction:column;min-height:100vh}
main{max-width:640px;width:100%;margin:0 auto;padding:24px 16px;flex:1}
h1{font-size:1.4rem;margin:0 0 16px}
h2{font-size:1.15rem;margin:16px 0}
.muted{color:#66707c;font-size:.9rem}
.top{display:flex;justify-content:space-between;gap:8px;font-weight:600}
.bar{height:6px;background:#e3e6ea;border-radius:3px;margin-top:8px;overflow:hidden}
#barFill{height:100%;background:#2563eb;width:0;transition:width .2s}
button{font:inherit;cursor:pointer;border:0;border-radius:8px;padding:12px 20px;background:#2563eb;color:#fff;font-weight:600;margin-top:12px}
button:disabled{cursor:default}
.opt{display:block;width:100%;text-align:left;background:#fff;color:#1d232b;border:1px solid #d5dae0;font-weight:400;margin-top:8px}
.opt:not(:disabled):hover{border-color:#2563eb}
.opt.correct{background:#e7f6ec;border-color:#1f8a4c}
.opt.wrong{background:#fdecec;border-color:#c62828}
#feedback{margin-top:16px;padding:12px;border-radius:8px;background:#fff;border:1px solid #d5dae0}
#feedback.ok strong{color:#1f8a4c}#feedback.bad strong{color:#c62828}
#verdict.pass{color:#1f8a4c}#verdict.fail{color:#c62828}
footer{text-align:center;font-size:.8rem;color:#66707c;padding:16px}