Untitled

dabblet.css

.test {
display: block;
position: absolute;
bottom: 0;
right: 0;
width: 0px;
height: 0px;
border-style: solid;
border-width: 0 0 200px 200px;
border-color: transparent transparent #007bff transparent;
line-height: 0px;
_border-color: #000000 #000000 #007bff #000000;
_filter: progid:DXImageTransform.Microsoft.Chroma(color='#000000');
border-radius: 0 0 0 0;
}
.test1 {
position: relative;
	width: 250px;
	height: 250px;
	border-radius: 5px;
	background: red;
}

dabblet.html

<div class="test1">
<a class="test"></a>
</div>

settings.json

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