# make the turtle graphics module available
import turtle

# also make the random module available
import random

# set up our graphical canvas
# width = 500, height = 500
turtle.setup(500, 500)

# get a stroke color
stroke = input("Enter a color for the stroke of your shape: ")

# make sure we have a valid stroke color before continuing
if stroke == "yellow" or stroke == "red" or stroke == "green" or stroke == "blue":

    # stroke is good!

    # get a fill color
    fill = input("Enter a color for the fill of your shape: ")

    # make sure the fill color is valid before continuing
    if fill == "yellow" or fill == "red" or fill == "green" or fill == "blue":

        # fill is good!

        # set the pen color
        turtle.pencolor(stroke)

        # set pen size
        turtle.pensize(5)

        # set our fill color
        turtle.fillcolor(fill)

        # start filling our shape
        turtle.begin_fill()

        # draw a square
        turtle.forward(100)
        turtle.right(90)
        turtle.forward(100)
        turtle.right(90)
        turtle.forward(100)
        turtle.right(90)
        turtle.forward(100)
        turtle.right(90)

        # stop filling our shape
        turtle.end_fill()

    # fill is bad!
    else:
        print ("Sorry, that's not a valid fill color")
        turtle.bye()

# stroke is invalid
else:
    print ("Sorry, that's not a valid color")
    turtle.bye()