Fixed menu for audiotheme obsidian theme

obsidian_fixed_menu.css

/**
 * These CSS rules make the menu fixed in audiotheme's obsidian theme (https://demo.audiotheme.com/obsidian/)
 * Note that the none-demo page probably does not have a bar above it at the top of the screen,
 * which means, that you might need to change the `top: 40px` into `top: 0`.
 */

@media (min-width: 768px) { /* prevent messing up the mobile menu */
    #menu-primary-menu {
        will-change: transform; /* ensure smooth scrolling */
        position: fixed; /* pin the menu bar to the screen */
        left: 0; /* menu bar starts at the left of the screen */
        top: 40px; /* move the menu bar below the demo bar */
        background: rgba(0, 0, 0, 0.8); /* prevent collision of fonts */
        max-width: 100%; /* ensure the menu bar takes full width, because of the background */
    }
}