# Kim Todd, CSE 142 Autumn 2008
# This program performs a graphical "random walk" on a DrawingPanel.

from random import *
from drawingpanel import *
from math import *

RADIUS = 75

# Moves by one step in a random direction; returns new position.
def step(x, y):
    dir = randint(0, 3)
    if dir == 0:    x += 1
    elif dir == 1:  x -= 1
    elif dir == 2:  y += 1
    else:           y -= 1
    return (x, y)

# Returns the distance between the given two points.
def distance((x1, y1), (x2, y2)):
    return sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)

# main
panel = DrawingPanel(RADIUS * 2, RADIUS * 2)
panel.canvas.create_oval(0, 0, RADIUS * 2, RADIUS * 2)
center = (RADIUS, RADIUS)
x, y = (RADIUS, RADIUS)

# loop until walker has exited the circle
while distance((x, y), center) < RADIUS:
    x, y = step(x, y)
    panel.canvas.create_rectangle(x, y, x + 1, y + 1, fill = "green")
    panel.sleep(10)