body {
    font-family: Arial, sans-serif;
    margin: 0;
    background: #f4f4f4;
    text-align: center;
}

header {
    background: #24292e;
    color: white;
    padding: 40px 20px;
}

.card {
    background: white;
    margin: 30px auto;
    padding: 20px;
    width: 80%;
    max-width: 500px;
    border-radius: 10px;
    box-shadow: 0 5px 10px rgba(0,0,0,0.1);
}

button {
    padding: 10px 20px;
    font-size: 16px;
    border: none;
    border-radius: 6px;
    background: #2ea44f;
    color: white;
    cursor: pointer;
}

button:hover {
    background: #22863a;
}

footer {
    margin-top: 40px;
    padding: 20px;
    background: #ddd;
}