Snake via Python Turtle

[@zhengli2589]

I strongly suggest everyone to try this optional Task for fun: Moving a black square around.
Please refer to the demo in the lecture video and try to move the black (or different color) square along different directions.
You may imagine this optional task in the context of this game Snake. But you are developing a never-growing snake.
Moving a black square is actually changing colors of different squares on a map. As the first step, you may try to make the same square “flash”, i.e. changing the color of the same square.
Please read and copy the following code of flashing a square to play a bit. Then try to “move” the square by yourself.
# Flashing a square
import time
import turtle
turtle.TurtleScreen._RUNNING = True
turtle.tracer(0, 0)
myPen=turtle.Turtle()
int_edge = 20
# Ten times flashing
for i in range(10):
# Start drawing a square in black
myPen.begin_fill()
myPen.penup()
myPen.goto(0,0) # Go to a particular position as the bottom left corner of the square
myPen.fillcolor("black")
myPen.pendown()
# Drawing four edges of the square
for k in range(4):
myPen.forward(int_edge)
myPen.left(90)
myPen.end_fill()
turtle.update()
# Finish drawing the square in black
time.sleep(0.5)
# Start drawing a square in white
myPen.begin_fill()
myPen.penup()
myPen.goto(0,0) # Go to a particular position as the bottom left corner of the square
myPen.fillcolor("white")
myPen.pendown()
# Drawing four edges of the square
for k in range(4):
myPen.forward(int_edge)
myPen.left(90)
myPen.end_fill()
turtle.update()
# Finish drawing the square in white
time.sleep(0.5)
myScreen = turtle.Screen()
myScreen.exitonclick()