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<!DOCTYPE html>
<html>
<head>
<title>FullScreen Button</title>
<style>
body, html {
margin: 0;
background-color: #3498db;
}
.btn {
width: 64px;
height: 64px;
background-color: #e74c3c;
position: absolute;
top: 50%;
left: 50%;
margin-top: -32px;
margin-left: -32px;
box-shadow: 0 0 0 2px #fff;
cursor: pointer;
transition: all .2s ease-out;
}
.btn:active {
background-color: #c0392b;
}
.part1, .part2 {
width: 32px;
height: 32px;
background-image: url(https://cdn0.iconfinder.com/data/icons/feather/96/591275-arrow-up-64.png);
background-size: 32px;
float: left;
transition: all .2s ease-out;
}
.part1 {
transform: rotate(-135deg);
position: relative;
top: 32px
}
.part2 {
transform: rotate(45deg);
}
.btn.fullscreen {
transform: scale(1.1);
}
.btn.fullscreen .part1 {
transform: rotate(45deg);
}
.btn.fullscreen .part2 {
transform: rotate(225deg);
}
</style>
</head>
<body>
<div class="btn">
<div class="part1"></div>
<div class="part2"></div>
</div>
<script>
document.querySelector('.btn').onclick = function () {
this.classList.toggle('fullscreen');
}
</script>
</body>
</html>