/**
 * Tiddlywinks — Back-to-top button visibility
 *
 * Pairs with back-to-top.js. main.css already positions #back-to-top
 * (fixed, top:85%, right:0 / 128px desktop) but always shows it. Here we only
 * control its show/hide so it fades in after the user scrolls down. Positioning
 * is intentionally left untouched.
 */
#back-to-top {
	opacity: 0;
	visibility: hidden;
	transition: opacity .3s ease, visibility .3s ease;
}

#back-to-top.tw-visible {
	opacity: 1;
	visibility: visible;
}