.app{max-width:640px;margin:4rem auto;padding:2rem;text-align:center;font-family:system-ui,sans-serif}button{padding:.6rem 1.2rem;font-size:1rem;border-radius:8px;border:1px solid #ccc;cursor:pointer}*{box-sizing:border-box}body{margin:0;background:#f5f5f5;color:#222}