body {
    margin: 0;
    font-family: Arial, sans-serif;
    background: #f4f4f4;
    color: #333;
}

header {
    background: #24292e;
    color: white;
    text-align: center;
    padding: 40px;
}

main {
    display: flex;
    justify-content: center;
    padding: 40px;
}

.card {
    background: white;
    padding: 30px;
    border-radius: 10px;
    box-shadow: 0 4px 10px rgba(0,0,0,.1);
    max-width: 500px;
    text-align: center;
}

button {
    background: #0366d6;
    color: white;
    border: none;
    padding: 12px 20px;
    border-radius: 5px;
    cursor: pointer;
}

button:hover {
    background: #024ea2;
}

footer {
    text-align: center;
    padding: 20px;
    color: #666;
}