style.css

body {
    margin: 0;
    padding: 0;
    font-family: arial;
}

.toggle {
    position: absolute;
    top: 40px;
    right: 50px;
    background: #fff;
    border: 2px solid #262626;
    width: 45px;
    height: 20px;
    cursor: pointer;
    transition: 0.5s;
    border-radius: 20px;
}

.toggle:before {
    content: '';
    position: absolute;
    top: 2px;
    left: 2px;
    width: 16px;
    height: 16px;
    background: #262626;
    border-radius: 50%;
    transition: 0.5s;
}
.toggle.active:before{
    left: 25px;
}

body.dark {
    background: #262626;
    transition: 0.8s;
}

.content {
    margin: 100px auto;
}
h2 {
	text-align: center;
    font-size:10vw;
    color: #000;
	font-family: arial;
	font-weight: bold;
	transition: .5s;
	text-transform: uppercase;
}
h2.dark {
    color: #f0c420;
}