// css clip
<div id="triangle"></div>
#triangle {
background-color: #003BDE;
clip-path: polygon(50% 0, 100% 100%, 0 100%);
width: 100px;
height: 100px;
}.triangle{
border-left: 5px solid transparent;
border-right: 5px solid transparent;
border-bottom: 5px solid red;
border-width:100px;
}#triangle {
width: 0;
height: 0;
border-left: 18px solid transparent;
border-right: 18px solid transparent;
border-bottom: 30px solid blue;
}div {
clip-path: polygon(100% 100%, 100% 100%, 100% 100%)
}#triangle-up {
width: 0;
height: 0;
border-left: 50px solid transparent;
border-right: 50px solid transparent;
border-bottom: 100px solid red;
}<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>Draw a circle</title>
</head>
<body onload="draw();">
<canvas id="circle" width="150" height="150"></canvas>
</body>
</html>