body{margin:0;font-family:sans-serif;background:#f5f5f5}.box{max-width:640px;margin:60px auto;padding:24px;background:#fff;border-radius:8px}button{margin-right:8px;padding:8px 14px;cursor:pointer}pre{margin-top:16px;padding:12px;background:#f0f0f0;overflow:auto}