Rocket.Chat/packages/rocketchat-tooltip/client/tooltip.css

.tooltip {
	position: absolute;
	z-index: 300;

	visibility: hidden;

	max-width: 400px;
	padding: 8px 10px;

	transition: opacity 0.3s ease;
	text-align: center;

	opacity: 0;
	color: #ffffff;
	border-radius: 5px;
	background: #000000;

	font-size: 0.8rem;

	&.show {
		visibility: visible;

		opacity: 0.9;
	}

	& .tooltip-arrow {
		position: absolute;
		top: 100%;
		left: 50%;

		width: 0;
		height: 0;
		margin-left: -5px;

		border-top: 5px solid #000000;
		border-right: 5px solid transparent;
		border-left: 5px solid transparent;
	}

	&.bellow {
		& .tooltip-arrow {
			top: -5px;

			border-top: none;
			border-bottom: 5px solid #000000;
		}
	}
}