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