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dabblet.css

body {
  padding: 20px;  
}
.triangle {
  width: 0;
  height: 0;
  border-right: 100px solid black;
  border-top: 20px solid transparent;
  border-bottom: 20px solid transparent;
  margin: 10px;
}
.smooth {
  transform: rotate(360deg);
}

dabblet.html

<div class="triangle"></div>

<div class="triangle smooth"></div>

settings.json

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