#!/usr/bin/env python
"""
 draw a Koch curve with the Turtle
"""

from turtle import Turtle

def koch(length, depth, max_depth, turtle):
    """ Recursively draw the Koch curve. """
    if depth >= max_depth:
        turtle.move(length)
    else:
        koch(length/3., depth+1, max_depth, turtle)
        turtle.turn(60)
        koch(length/3., depth+1, max_depth, turtle)
        turtle.turn(-120)
        koch(length/3., depth+1, max_depth, turtle)
        turtle.turn(60)
        koch(length/3., depth+1, max_depth, turtle)

size_across = 1000
size_high   =  350
starting_length = size_across - 100
starting_depth = 0
depth_limits = (0, 6)

prompt = "Koch curve from depth=0 to ? (%i..%i) " % depth_limits
max_depth = input(prompt)
if max_depth < depth_limits[0]: max_depth = depth_limits[0]
if max_depth > depth_limits[1]: max_depth = depth_limits[1]

t = Turtle(width=size_across, height=size_high)
t.x = -size_across/2 + 50
t.y = -size_high/2 + 50

koch(starting_length, starting_depth, max_depth, t)

wait = raw_input("Hit return to quit.")