body,html{text-align:center}#app{display:flex;height:200px;justify-content:center;align-items:center;flex-direction:column}#open-app{display:none;padding:10px 20px;font-size:16px;color:#000;border:1px solid #f0f0f0;border-radius:5px;cursor:pointer;transition:background-color .3s ease}#error-message{font-size:12px;display:none;margin-top:10px}