*{box-sizing:border-box}body{margin:0;font-family:system-ui,Arial,PingFang SC,Microsoft YaHei,sans-serif}.container{max-width:720px;margin:10vh auto;padding:24px;border-radius:16px;box-shadow:0 10px 30px #00000014;transition:background .3s,color .3s}body.light{background:#f5f5f5;color:#222}body.light .container{background:#fff}body.dark{background:#222;color:#eee}body.dark .container{background:#333}button{padding:10px 16px;font-size:16px;border:0;border-radius:10px;cursor:pointer}button:hover{filter:brightness(1.08)}#counterText{margin-top:12px}