body{margin:0;font-family:Arial,sans-serif;background:#111;color:#fff;text-align:center}header{padding:20px;background:#222;font-size:24px}button{padding:15px 25px;font-size:18px;border:none;border-radius:8px;background:#fc0;color:#000;cursor:pointer;margin-top:40px}button:hover{background:#fd3}.hidden{display:none}#result{margin-top:30px;font-size:20px}