Hola compañero genial tu codigo, yo tambien comparto el mio aqui :3
<canvas width="600" height="400">
</canvas>
<script>
var pantalla = document.querySelector("canvas");
var pincel = pantalla.getContext("2d");
pincel.fillStyle = "white";
pincel.fillRect(0,0,600,400);
pincel.fillStyle = "darkgreen";
pincel.fillRect(125,35,350,300); //1
pincel.fillStyle = "black";
pincel.fillRect(175,95,90,90); //2
pincel.fillStyle = "black";
pincel.fillRect(335,95,90,90); //3
pincel.fillStyle = "black";
pincel.fillRect(265,185,70,100); //4
pincel.fillStyle = "black";
pincel.fillRect(225,225,40,110); //5
pincel.fillStyle = "black";
pincel.fillRect(335,225,40,110); //6
</script>