src/librustdoc/html/static/settings.css

.setting-line {
	padding: 5px;
}

.setting-line > div {
	max-width: calc(100% - 74px);
	display: inline-block;
	vertical-align: top;
	font-size: 17px;
	padding-top: 2px;
}

.toggle {
	position: relative;
	display: inline-block;
	width: 45px;
	height: 27px;
	margin-right: 20px;
}

.toggle input {
	display: none;
}

.slider {
	position: absolute;
	cursor: pointer;
	top: 0;
	left: 0;
	right: 0;
	bottom: 0;
	background-color: #ccc;
	-webkit-transition: .3s;
	transition: .3s;
}

.slider:before {
	position: absolute;
	content: "";
	height: 19px;
	width: 19px;
	left: 4px;
	bottom: 4px;
	background-color: white;
	-webkit-transition: .3s;
	transition: .3s;
}

input:checked + .slider {
	background-color: #2196F3;
}

input:focus + .slider {
	box-shadow: 0 0 1px #2196F3;
}

input:checked + .slider:before {
	-webkit-transform: translateX(19px);
	-ms-transform: translateX(19px);
	transform: translateX(19px);
}