Rocket.Chat/app/theme/client/imports/components/sidebar/sidebar.css

.sidebar {

	position: relative;

	z-index: 2;

	display: flex;
	flex-direction: column;
	flex: 0 0 var(--sidebar-width);

	width: var(--sidebar-width);
	max-width: var(--sidebar-width);

	height: 100%;

	user-select: none;

	transition: transform 0.3s;

	background-color: var(--sidebar-background);

	&-wrap {
		position: absolute;
		z-index: 1;
		top: 0;
		left: 0;

		height: 100%;

		user-select: none;
		transition: opacity 0.3s;
		-webkit-tap-highlight-color: rgba(0, 0, 0, 0);
		touch-action: pan-y;
		-webkit-user-drag: none;
	}

	&__footer:not(:empty) {
		width: auto;
		height: var(--sidebar-footer-height);
		padding: var(--sidebar-extra-small-default-padding) var(--sidebar-default-padding);

		& img {
			max-width: 100%;
			height: 100%;
		}

		& a:any-link {
			color: var(--rc-color-primary-light);
		}
	}

	& .wrapper-unread {
		position: relative;
		z-index: 2;

		& .unread-rooms {
			position: absolute;
			left: 50%;

			overflow: hidden;

			min-width: 120px;
			max-width: 100%;

			padding: 8px var(--sidebar-small-default-padding);

			-webkit-transform: translateX(-50%);
			transform: translateX(-50%);

			animation: fade 0.3s;

			text-align: center;

			white-space: nowrap;

			text-overflow: ellipsis;

			border-radius: 25px;

			&.bottom-unread-rooms {
				bottom: 0;
			}

			&.top-unread-rooms {
				top: 0;
			}
		}
	}
}

@keyframes fade {
	from {
		opacity: 0;
	}

	to {
		opacity: 1;
	}
}

@media (width < 768px) {
	.sidebar {
		position: absolute;

		user-select: none;
		transform: translate3d(-100%, 0, 0);
		-webkit-tap-highlight-color: rgba(0, 0, 0, 0);
		touch-action: pan-y;
		-webkit-user-drag: none;
		will-change: transform;
	}

	.rtl .sidebar {
		transform: translate3d(200%, 0, 0);
	}
}

@media (width <= 400px) {
	.sidebar {
		flex: 0 0 var(--sidebar-small-width);

		width: var(--sidebar-small-width);
		max-width: var(--sidebar-small-width);

		&__footer {
			display: none;
		}

		&:not(&--light) {
			transform: translate3d(-100%, 0, 0);
		}
	}

	.rtl .sidebar {
		transform: translate3d(200%, 0, 0);
	}
}

@media (min-width: 1372px) { /* 1440px -68px (eletron menu) */
	.sidebar {
		flex: 0 0 20%;

		width: 20%;
		max-width: 20%;
	}
}