The first commented line is your dabblet’s title

dabblet.css

/**
 * The first commented line is your dabblet’s title
 */
body {
	margin:0;
	background:rgb(0,0,20);
}
#light {
	position:relative; 
	width:0;
	height:0;
	margin-left:12px;

}
#light:before {
	content:"";
	width: 0;
	height: 0;
	display:block;
	border-left: 25px solid transparent;
	border-right: 0px solid transparent;
	border-bottom: 65px solid yellow;
	
	transform:skewx(-20deg);
}


#light:after {
	content:"";
	width: 0;
	height: 0;
	display:block;
	border-left: 25px solid transparent;
	border-right: 0px solid transparent;
	border-bottom: 65px solid yellow;
	
	transform:skewx(-20deg) rotate(180deg) translateY(20px);
}

dabblet.html

<div id="light"></div>

settings.json

{"view":"split","seethrough":"","prefixfree":"1","page":"css"}