body {
    font-family: sans-serif;
    margin: 0;
    background: #f5f5f5;
    text-align: center;
}

header {
    background: #333;
    color: white;
    padding: 10px;
}

header a {
    color: white;
    margin: 0 8px;
    text-decoration: none;
}

main {
    padding: 20px;
}

.start-btn {
    display: inline-block;
    margin-top: 20px;
    padding: 12px 24px;
    background: #2196f3;
    color: white;
    text-decoration: none;
    border-radius: 6px;
}

#game-area {
    margin-top: 20px;
}

.number-btn {
    width: 60px;
    height: 60px;
    margin: 5px;
    font-size: 18px;
}

footer {
    margin-top: 40px;
    font-size: 12px;
    color: #666;
}