Draw some pretty cubes 

necker-grid.pyde

from random import randrange

size(600,600)
background(255)
strokeWeight(2)

rowheight = height/7
colwidth = width/6

for y in range(0,height+rowheight,rowheight):
    y = y-90
    for x in range(0,width+colwidth,colwidth):
        x = x-90
        fillcolr = color(randrange(255),randrange(255),randrange(255),50)
        noFill()
        noStroke()
        # 1. draw a square in the center of the window
        rect(x+100,y+100, 50,50)
        # # 2. draw another square of the same size starting in the center of the first rectangle
        rect(x+125,y+125, 50,50)
        # # 3. draw a line from the NW corners
        line(x+100,y+100,x+125,y+125)
        # # 4. draw a line from the NE corners
        line(x+150,y+100, x+175,y+125)
        # # 5. draw a line from the SW corners
        line(x+100,y+150, x+125,y+175)
        # # 6. draw a final line from the SE corners
        line(x+150,y+150, x+175,y+175)
        # draw the planes
        stroke(255)
        fill(fillcolr)
        rect(x+100,y+100, 50,50)
        rect(x+125,y+125, 50,50)
        quad(x+100,y+100, x+125,y+125, x+125,y+175, x+100,y+150)
        quad(x+100,y+100, x+150,y+100, x+175,y+125, x+125,y+125)
        quad(x+150,y+100, x+175,y+125, x+175,y+175, x+150,y+150)
        quad(x+150,y+150, x+175,y+175, x+125,y+175, x+100,y+150)