<!doctype html>
<html lang="en">
    <head>
        <script src="http://play.workadventure.localhost/iframe_api.js"></script>
    </head>
    <body>
    	<div>
            <label for="show/hideLayer">Crysal Layer : </label><input type="checkbox" id="show/hideLayer" name="visible" value="show" checked>
        </div>
    	<script>
    		document.getElementById('show/hideLayer').onclick = () => {
                if (document.getElementById('show/hideLayer').checked) {
                    WA.room.showLayer('crystal');
                }
                else {
                    WA.room.hideLayer('crystal');
                }
            }
    	</script>
    </body>
</html>