<canvas width="350" height="300"> </canvas>
<script>
var pantalla = document.querySelector("canvas");
var pincel = pantalla.getContext("2d");
pincel.fillStyle = "darkgreen"
pincel.fillRect(0,0,600,500);
pincel.fillStyle = "black"
pincel.beginPath();
pincel.fillRect(50,60,90,90);
pincel.fillStyle = "black"
pincel.fillRect(210,60,90,90);
pincel.fillStyle = "black"
pincel.fillRect(140,150,70,100,);
pincel.fillStyle = "black"
pincel.fillRect(100,200,40,110);
pincel.fillStyle = "black"
pincel.fillRect(210,200,40,110);
</script>
