Create a generally smooth gradation of white to black, from left to right using only a 100 percent black pen.

#
# a program that builds to a gradient effect, from white on the 
# to black on the right. the effect is made by varying the density
# of black lines, which the build-up helps to emphasize.

def hlines (y):
 g.line(0, y*9, 100, y)

g.paper(0)
g.pen(100)
g.norefresh()
for y in range (0, 100):
 hlines(y+(y*2))
g.refresh()
g.pause(50)

g.pause(50)
g.line(0, 117, 100, 13)
g.norefresh()
for y in range (0, 100):
 hlines(y+(y*3))
g.refresh()

g.pause(50)
g.norefresh()
for y in range (0, 200):
 hlines(y+(y/6))
g.refresh()