<canvas width="600" height="400"> </canvas>
<script>
var pizarra = document.querySelector ("canvas");
var pincel = pizarra.getContext ("2d");
pincel.fillStyle = "darkgreen";
pincel.fillRect (0,0,350,300);
pincel.fillStyle = "black";
pincel.fillRect (55,60,90, 90);
pincel.fillRect (215, 60, 90, 90);
pincel.fillRect (145, 150, 70, 100);
pincel.fillRect (105,200,40,100);
pincel.fillRect (215,200,40,100);
</script>