main{max-width:600px;margin:0 auto;padding:20px;font-family:Arial,sans-serif}a{color:#007bff}input,button{width:100%;padding:10px;margin:10px 0;box-sizing:border-box}input[type=checkbox]{width:auto;margin-right:10px}section,form{max-width:400px;margin:0 auto}ul li{margin-top:4px}