#----------------------------------------------------------------------
# Sierpinski Gasket
#
# Copyright (C) March 2, 2018 -- Dr. William T. Verts
#
# Here the code has been rewritten to use points (lists of [X,Y]
# coordinates).  This requires a function to compute the average
# of two points.  All the rest of the code is now based off of
# lists as well: Points is a list of the three triangle vertices,
# and Colors is a list of the three corner colors.  Rather than
# explicitly test if N==0, if N==1, etc., we now use N as the
# index into the lists.  The code packs down considerably as a
# result.
#----------------------------------------------------------------------

import random

def Average (P,Q):          # P and Q are both [X,Y] points
    X = (P[0] + Q[0]) / 2
    Y = (P[1] + Q[1]) / 2
    return [X,Y]


Canvas = makeEmptyPicture(640,480)
P0 = [getWidth(Canvas) / 2,0]
P1 = [0,getHeight(Canvas) - 1]
P2 = [getWidth (Canvas) - 1,getHeight(Canvas) - 1]
PP = [P0[0],P0[1]]
Points = [P0,P1,P2]
Colors = [magenta,cyan,yellow]
Counter = 0

while True:
    N = random.randint(0,2)
    PP = Average(PP, Points[N])
    setColor(getPixel(Canvas,PP[0],PP[1]),Colors[N])    
    Counter = Counter + 1
    if (Counter >= 1000):
        repaint(Canvas)
        Counter = 0