<canvas width="600" height="400"> </canvas>
<script>
var pantalla = document.querySelector("canvas");
var pincel = pantalla.getContext ("2d");
pincel.fillStyle = "darkgreen";
pincel.fillRect(0,0,350,300);
pincel.fillStyle = "black";
pincel.fillRect(50,50,90,90);
pincel.fillStyle = "black";
pincel.fillRect(210,50,90,90);
pincel.fillStyle = "black";
pincel.fillRect(140,140,70,100);
pincel.fillStyle = "black";
pincel.fillRect(100,190,40,110);
pincel.fillStyle = "black";
pincel.fillRect(210,190,40,110);
</script>
