body {
    font-family: Tahoma, sans-serif;
    margin: 0;
    padding: 0;
    color: #fff;
    text-align: center;
}

.login-container, .guest-container {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: rgba(0,0,0,0.6);
    padding: 30px;
    border-radius: 10px;
}

input {
    display: block;
    margin: 10px auto;
    padding: 10px;
    width: 80%;
}

button {
    padding: 10px 20px;
    cursor: pointer;
}