body {
    margin: 0;
    font-family: monospace;
}

button {
    font-family: monospace;
}

ul {
    font-size: 1.5em;
    text-align: left;
    list-style-type: none;
    margin: 0;
    padding: 0;
    width: 17%;
    background-color: #f1f1f1;
    position: fixed;
    height: 100%;
    overflow: auto;
}

li a {
    display: block;
    color: #000;
    padding: 8px 16px;
    text-decoration: none;
}

li a.active {
    background-color: #3684e0;
    color: white;
}

li a:hover:not(.active) {
    background-color: #555;
    color: white;
}

#mainContainer {
    position: fixed;
    margin-left: 17%;
    height: 100%;
    width: 83%;
    text-align: center;
    overflow: auto;
}