mobile-config-firefox/src/userChrome/appMenu.css

/* Copyright 2021 Oliver Smith
 * SPDX-License-Identifier: GPL-3.0-or-later */

@media (max-width: 700px) {
    .subviewbutton,
    .toolbaritem-combined-buttons {
        font-size: 8pt;
    }

    #appMenu-protection-report-button,
    #appMenuRestoreLastSession,
    #appMenu-customize-button,
    #appMenu-open-file-button,
    #appMenu-more-button,
    #appMenu-developer-button,
    #appMenu-whatsnew-button,
    #appMenu-help-button,
    #appMenu-quit-button {
        display: none;
    }

    toolbarseparator {
        display: none;
    }

    /* Zoom/edit: move controls to the left (so they are visible), hide
     * label (it's obvious what they do) and spacer */
    #appMenu-zoom-controls spacer,
    #appMenu-zoom-controls label,
    #appMenu-edit-controls spacer,
    #appMenu-edit-controls label {
        display: none;
    }

    /* Zoom/edit: center the controls somewhat */
    #appMenu-zoom-controls {
        padding-left: 20px;
    }
    #appMenu-edit-controls {
        padding-left: 15px;
    }

    /* Zoom: hide fullscreen button (not possible to exit fullscreen
     * without keyboard) */
    #appMenu-fullscreen-button {
        display: none;
    }
}