'''Program to draw a Koch fractal using turtle graphics
and recursion.'''

import turtle

# length of a side of the triangle
SIDE_LEN = 300


def draw_side(size, order):
    '''Draw one side of the triangle of length size, 
    where the side is an order 'order' fractal.'''

    if order == 0:
        # base case - order 0 fractal (straight line)
        turtle.forward(size)
    else:
        # recursive case - four order n - 1 fractals
        draw_side(size / 3, order - 1)
        turtle.left(60)
        draw_side(size / 3, order - 1)
        turtle.right(120)
        draw_side(size / 3, order - 1)
        turtle.left(60)
        draw_side(size / 3, order - 1)


def main():
    turtle.up()
    turtle.goto(-SIDE_LEN/2, SIDE_LEN/2)
    turtle.down()
    
    turtle.speed('fastest')
    
    for i in range(3):
        draw_side(SIDE_LEN, 3)
        turtle.right(120)

main()