#!/usr/bin/python

"""       turtle-example-suite:

         tdemo_minimal_hanoi.py

A minimal 'Towers of Hanoi' animation:

A tower of 6 discs is transferred from the

left to the right peg.

An imho quite elegant and concise

implementation using a tower class, which

is derived from the built-in type list.

Discs are turtles with shape "square", but

stretched to rectangles by shapesize()

 ---------------------------------------

       To exit press STOP button

 ---------------------------------------

"""

from turtle import *

class Disc(Turtle):

    def __init__(self, n):

        Turtle.__init__(self, shape="square", visible=False)

        self.pu()

        self.shapesize(1.5, n*1.5, 2) # square-->rectangle

        self.fillcolor(n/6., 0, 1-n/6.)

        self.st()

class Tower(list):

    "Hanoi tower, a subclass of built-in type list"

    def __init__(self, x):

        "create an empty tower. x is x-position of peg"

        self.x = x

    def push(self, d):

        d.setx(self.x)

        d.sety(-150+34*len(self))

        self.append(d)

    def pop(self):

        d = list.pop(self)

        d.sety(150)

        return d

def hanoi(n, from_, with_, to_):

    if n > 0:

        hanoi(n-1, from_, to_, with_)

        to_.push(from_.pop())

        hanoi(n-1, with_, from_, to_)

def play():

    onkey(None,"space")

    clear()

    hanoi(6, t1, t2, t3)

    write("press STOP button to exit",

          align="center", font=("Courier", 16, "bold"))

def main():

    global t1, t2, t3

    ht(); penup(); goto(0, -225)   # writer turtle

    t1 = Tower(-250)

    t2 = Tower(0)

    t3 = Tower(250)

    # make tower of 6 discs

    for i in range(6,0,-1):

        t1.push(Disc(i))

    # prepare spartanic user interface ;-)

    write("press spacebar to start game",

          align="center", font=("Courier", 16, "bold"))

    onkey(play, "space")

    listen()

    return "EVENTLOOP"

if __name__=="__main__":

    msg = main()

    print msg

    mainloop()