mdBook/data/assets/_html-template/_stylus/theme-popup.styl

.theme-popup {
    position: relative
    left: 10px

    z-index: 1000;

    border-radius: 4px
    font-size: 0.7em

    .theme {
        margin: 0
        padding: 2px 10px
        line-height: 25px
        white-space: nowrap

        &:hover:first-child,
        &:hover:last-child {
            border-top-left-radius: inherit;
            border-top-right-radius: inherit;
        }
    }

}

@media only screen and (max-width: 1250px) {

    .nav-chapters {
        display: none
    }

    .mobile-nav-chapters {
        font-size: 2.5em
        text-align: center
        text-decoration: none

        max-width: 150px
        min-width: 90px

        justify-content: center
        align-content: center

        position: relative
        display: inline-block
        margin-bottom: 50px

        border-radius: 5px
    }

    .next {
        float: right
    }

    .previous {
        float: left
    }
}