#!/usr/bin/env python3
""" turtle-example-suite:

 tdemo_paint.py

A simple event-driven paint program

- left mouse button moves turtle
- middle mouse button changes color
- right mouse button toggles between pen up
(no line drawn when the turtle moves) and
pen down (line is drawn). If pen up follows
at least two pen-down moves, the polygon that
includes the starting point is filled.
 -------------------------------------------
 Play around by clicking into the canvas
 using all three mouse buttons.
 -------------------------------------------
 To exit press STOP button
 -------------------------------------------
"""
from turtle import *

def switchupdown(x=0, y=0):
 if pen()["pendown"]:
 end_fill()
 up()
 else:
 down()
 begin_fill()

def changecolor(x=0, y=0):
 global colors
 colors = colors[1:]+colors[:1]
 color(colors[0])

def main():
 global colors
 shape("circle")
 resizemode("user")
 shapesize(.5)
 width(3)
 colors=["red", "green", "blue", "yellow"]
 color(colors[0])
 switchupdown()
 onscreenclick(goto,1)
 onscreenclick(changecolor,2)
 onscreenclick(switchupdown,3)
 return "EVENTLOOP"

if __name__ == "__main__":
 msg = main()
 print(msg)
 mainloop()