```python
def setup():
py5.size(100, 100, py5.P3D)
def draw():
py5.background(204)
x = py5.mouse_x
y = py5.mouse_y
z = -100
# draw "X" at z = -100
py5.stroke(255)
py5.line(x-10, y-10, z, x+10, y+10, z)
py5.line(x+10, y-10, z, x-10, y+10, z)
# draw gray line at z = 0 and same
# y value. notice the parallax
py5.stroke(102)
py5.line(0, y, 0, py5.width, y, 0)
# draw black line at z = 0 to match
# the y value element drawn at z = -100
py5.stroke(0)
the_y = py5.screen_y(x, y, z)
py5.line(0, the_y, 0, py5.width, the_y, 0)
```