# set the current fill color
# the three numbers are values for
# red, green and blue (RGB)
# the values are numbers between
# 0 and 1
fill(0, 0, 0.75)

# draw two rectangles
rect(50, 50, 150, 250)
rect(150, 150, 150, 250)


# set a color
# note the fourth number: it's the
# transparency
fill(1, 0, 0, 0.25)
rect(250, 250, 150, 250)
rect(350, 350, 150, 250)