bigbluebutton-Github/bigbluebutton-html5/imports/ui/stylesheets/mixins/_scrollable.scss

@mixin scrollbox-vertical($bg-color: white) {
  overflow-y: auto;
  background: linear-gradient($bg-color 30%, rgba(255,255,255,0)),
		linear-gradient(rgba(255,255,255,0), $bg-color 70%) 0 100%,

		/* Shadows */
		radial-gradient(farthest-side at 50% 0, rgba(0,0,0,.2), rgba(0,0,0,0)),
		radial-gradient(farthest-side at 50% 100%, rgba(0,0,0,.2), rgba(0,0,0,0)) 0 100%;

  background-repeat: no-repeat;
  background-color: transparent;
  background-size: 100% 40px, 100% 40px, 100% 14px, 100% 14px;
  background-attachment: local, local, scroll, scroll;

  :global(.browser-edge) & {
    background: none;
  }

	// Fancy scroll
  &::-webkit-scrollbar {
    width: 5px;
    height: 5px;
  }
  &::-webkit-scrollbar-button {
    width: 0;
    height: 0;
  }
  &::-webkit-scrollbar-thumb {
    background: rgba(0,0,0,.25);
    border: none;
    border-radius: 50px;
  }
  &::-webkit-scrollbar-thumb:hover { background: rgba(0,0,0,.5); }
  &::-webkit-scrollbar-thumb:active { background: rgba(0,0,0,.25); }
  &::-webkit-scrollbar-track {
    background: rgba(0,0,0,.25);
    border: none;
    border-radius: 50px;
  }
  &::-webkit-scrollbar-track:hover { background: rgba(0,0,0,.25); }
  &::-webkit-scrollbar-track:active { background: rgba(0,0,0,.25); }
  &::-webkit-scrollbar-corner { background: 0 0; }
}