body{color:#111;background:#fff;margin:0;font-family:Arial,Helvetica,sans-serif}header{text-align:center;border-bottom:1px solid #eee;padding:1rem}nav a{color:#0070f3;margin:0 .75rem;text-decoration:underline}main{flex-direction:column;align-items:center;padding:2rem;display:flex}h1{margin-bottom:1rem;font-size:1.25rem}button{color:#fff;cursor:pointer;background:#111;border:none;margin-bottom:1rem;padding:.6rem 1.2rem;font-size:1rem}button:disabled{opacity:.5;cursor:not-allowed}p{margin:.25rem 0}