body {
 font-family: Arial, sans-serif;
 margin: 0 auto;
 padding: 2em;
 max-width: 600px;
 text-align: center;
}

button {
 background-color: #4CAF50;
 color: white;
 padding: 10px 20px;
 border-radius: 5px;
 cursor: pointer;
}

button:hover {
 background-color: #3e8e41;
}

#login-form {
 display: none;
}

#login-form.open {
 display: block;
}