Untitled

dabblet.css

div{
	height:300px;width:300px;background:red;
	-webkit-mask-position: 0 0;
    -webkit-mask-size: 100%;
    -webkit-mask-image: -webkit-gradient(linear, left top, right bottom, 
   color-stop(0.00,  rgba(0,0,0,1)),
   color-stop(0.50,  rgba(0,0,0,1)),
   color-stop(0.50,  rgba(0,0,0,0)),
   color-stop(1.00,  rgba(0,0,0,0)));
}

dabblet.html

<div></div>

settings.json

{"view":"split","fontsize":"100","seethrough":"","prefixfree":"1","page":"all"}