body{font-family:Arial,sans-serif;margin:0;padding:0;background-color:#f4f4f4}header{background:#333;color:#fff;padding:1rem;text-align:center}main{padding:1rem;margin:2rem auto;max-width:600px;background:#fff;box-shadow:0 0 10px #0000001a}.puzzle{margin:1rem 0}input{margin-left:10px;width:30px;text-align:center}