body {
    background: #111;
    color: #fff;
    font-family: Arial, sans-serif;
    text-align: center;
    margin: 0;
    padding: 20px;
}

.menu {
    margin-bottom: 20px;
}

.menu a {
    color: #fff;
    text-decoration: none;
    margin: 0 10px;
    padding: 6px 12px;
    border: 1px solid #555;
    border-radius: 4px;
}

.menu a:hover {
    background: #333;
}

.key {
    display: inline-flex;
    width: 50px;
    height: 200px;
    margin: 4px;
    background: #eee;
    color: #000;
    align-items: flex-end;
    justify-content: center;
    border-radius: 4px;
    padding-bottom: 8px;
}

.key.active {
    background: #ccc;
}

#piano, #guitar {
    display: flex;
    justify-content: center;
    margin-top: 20px;
    min-height: 220px;
}