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

header {
    background: #333;
    color: white;
    padding: 1em;
}

nav a {
    color: white;
    text-decoration: none;
    margin: 0 10px;
}

nav a:hover {
    text-decoration: underline;
}

main {
    padding: 20px;
}

footer {
    background: #333;
    color: white;
    padding: 1em;
    position: absolute;
    width: 100%;
    bottom: 0;
}

button {
    padding: 10px 20px;
    border: none;
    background: #007bff;
    color: white;
    cursor: pointer;
    font-size: 16px;
}

button:hover {
    background: #0056b3;
}

.popup {
    display: none;
    position: fixed;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
}

.popup-content {
    background: white;
    margin: 15% auto;
    padding: 20px;
    width: 300px;
    position: relative;
    text-align: center;
}

.close {
    position: absolute;
    top: 5px;
    right: 10px;
    cursor: pointer;
    font-size: 20px;
}