devshell/theme/pagetoc.css

:root {
    --toc-width: 310px;
    --center-content-toc-shift: calc(-1 * var(--toc-width) / 2);
}

.nav-chapters {
    /* adjust width of buttons that bring to the previous or the next page */
    min-width: 50px;
}

.previous {
    /*
    adjust the space between the left sidebar or the left side of the screen 
    and the button that leads to the previous page
    */
    margin-left: var(--page-padding);
}

@media only screen {
    main {
        display: flex;
    }

    @media (max-width: 1219px) {
        .sidebar-hidden .sidetoc {
            display: none;
        }
    }

    @media (max-width: 1499px) {
        .sidebar-visible .sidetoc {
            display: none;
        }
    }

    @media (1220px <= width <= 1519px) {
        .sidebar-hidden main {
            position: relative;
            left: var(--center-content-toc-shift);
        }
    }

    @media (1500px <= width <= 1820px) {
        .sidebar-visible main {
            position: relative;
            left: var(--center-content-toc-shift);
        }
    }

    .content-wrap {
        overflow-y: auto;
        width: 100%;
    }

    .sidetoc {
        margin-top: 20px;
        margin-left: 10px;
        margin-right: auto;
    }
    .pagetoc {
        position: fixed;
        /* adjust TOC width */
        width: var(--toc-width);
        height: calc(100vh - var(--menu-bar-height) - 0.67em * 4);
        overflow: auto;
    }
    .pagetoc a {
        border-left: 1px solid var(--sidebar-bg);
        color: var(--fg) !important;
        display: block;
        padding-bottom: 5px;
        padding-top: 5px;
        padding-left: 10px;
        text-align: left;
        text-decoration: none;
    }
    .pagetoc a:hover,
    .pagetoc a.active {
        background: var(--sidebar-bg);
        color: var(--sidebar-fg) !important;
    }
    .pagetoc .active {
        background: var(--sidebar-bg);
        color: var(--sidebar-fg);
    }
    .pagetoc .pagetoc-H2 {
        padding-left: 20px;
    }
    .pagetoc .pagetoc-H3 {
        padding-left: 40px;
    }
    .pagetoc .pagetoc-H4 {
        padding-left: 60px;
    }
}

@media print {
    .sidetoc {
        display: none;
    }
}