<meta charset="utf-8">
<canvas width="600" height="400"> </canvas>
<script type="text/javascript">
var tela = document.querySelector('canvas');
var pincel = tela.getContext('2d');
pincel.fillStyle = "black";
pincel.beginPath();
pincel.moveTo(50, 50);
pincel.lineTo(50, 400);
pincel.lineTo(400,400);
pincel.fill();
pincel.fillStyle = "white";
pincel.beginPath();
pincel.moveTo(100,350);
pincel.lineTo(100,175);
pincel.lineTo(275,350);
pincel.fill();
</script>
