body {
    font-family: Arial, sans-serif;
    max-width: 400px;
    margin: 50px auto;
    padding: 20px;
    background-color: #f5f5f5;
}
.container {
    background: white;
    padding: 30px;
    border-radius: 10px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    text-align: center;
    align-items: center;
    justify-content: center;
}
.form-group {
    margin-bottom: 15px;
}
label {
    display: block;
    margin-bottom: 5px;
    font-weight: bold;
}
input[type="text"], input[type="password"] {
    width: 100%;
    padding: 10px;
    border: 1px solid #ddd;
    border-radius: 5px;
    box-sizing: border-box;
}
button {
    width: 100%;
    padding: 12px;
    margin: 5px 0;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-size: 16px;
}
.btn-login {
    background-color: #007bff;
    color: white;
}
.btn-yellow {
    background-color: #e0d63d;
    color: white;
}
.btn-register {
    background-color: #28a745;
    color: white;
}
.btn-logout {
    background-color: #dc3545;
    color: white;
}
button:hover {
    opacity: 0.9;
}
.message {
    padding: 10px;
    margin: 10px 0;
    border-radius: 5px;
}
.success {
    background-color: #d4edda;
    color: #155724;
    border: 1px solid #c3e6cb;
}
.error {
    background-color: #f8d7da;
    color: #721c24;
    border: 1px solid #f5c6cb;
}
.welcome {
    text-align: center;
    color: #000000;
}