var pantalla = document.querySelector("canvas");
var pincel = pantalla.getContext("2d");
pincel.fillStyle = "darkgreen"; //propiedad
pincel.fillRect(0,0,350,300); //función
pincel.fillStyle = "black";
pincel.fillRect(50,50,90,90);
pincel.fillRect(200,50,90,90);
pincel.fillRect(135,140,70,100);
pincel.fillRect(95,190,40,110);
pincel.fillRect(205,190,40,110);
</script>