* {
    box-sizing: border-box;
}

#sidebar {
    position: fixed;
    left: 0;
    top: 0;
    width: 260px;
    height: 100vh;
    padding: 1rem;
    border-left: 1px solid #ccc;
    background: #111;
    color: white;
    overflow-y: auto;
    padding-bottom: 2rem;
}

#content {
    margin-left: 290px;
    padding: 2rem;
}

#sidebar button {
    display: block;
    width: 100%;
    background: none;
    color: inherit;
    border: none;
    text-align: left;
    padding: 0.35rem 0;
    cursor: pointer;
}

.submenu {
    display: none;
    margin-left: 1rem;
    border-left: 1px solid #444;
    padding-left: 0.75rem;
}

.submenu.open {
    display: block;
}

.nested {
    margin-left: 1.25rem;
}

math-field {
    border: none;
    outline: none;
    box-shadow: none;
}