def setup():
 size(100, 100, P3D)
def draw():
 background(204)
 x = mouseX
 y = mouseY
 z = -100
 # Draw "X" at z = -100
 stroke(255)
 line(x - 10, y - 10, z, x + 10, y + 10, z)
 line(x + 10, y - 10, z, x - 10, y + 10, z)
 # Draw gray line at z = 0 and same
 # x value. Notice the parallax
 stroke(102)
 line(x, 0, 0, x, height, 0)
 # Draw black line at z = 0 to match
 # the x value element drawn at z = -100
 stroke(0)
 theX = screenX(x, y, z)
 line(theX, 0, 0, theX, height, 0)