<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
:fullscreen {
background-color: yellow;
}
button {
padding: 10px;
font-size: 15px;
}
</style>
</head>
<body>
<h2>Fullscreen Mode</h2>
<p>Click on the "Open Fullscreen" button to open this page in fullscreen mode. Close it by either clicking the "Esc" key on your keyboard, or with the "Close Fullscreen" button.</p>
<button onclick="openFullscreen();">Open Fullscreen</button>
<button onclick="closeFullscreen();">Close Fullscreen</button>
<script>
const elem = document.documentElement;
function openFullscreen() {
if (elem.requestFullscreen) {
elem.requestFullscreen();
}
}
function closeFullscreen() {
if (document.exitFullscreen) {
document.exitFullscreen();
}
}
</script>
</body>
</html>