body {
    transition: background-color 0.5s ease;
    background-color: #f0f0f0;
}
.login-container {
    margin-top: 100px;
}
.login-box {
    max-width: 400px;
    margin: auto;
    background: #fff;
    padding: 30px;
    border-radius: 8px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}
.btn-change-background {
    font-size: 16px;
    padding: 10px 20px;
    margin-top: 20px;
}
.login-box h3 {
    margin-bottom: 30px;
    text-align: center;
}
.form-group input {
    font-size: 16px;
}