Know Your Boundaries, Turtle

Currently, with our turtle game, you can move your player turtle off the screen, which we don’t want to happen, in this exercise, we are going to draw a border and then set boundaries so your turtle can not move off the screen.

Step 1.

Use Save As to save your module as kbgame3

Step 2.

Move to the top of your code just under the #Set up Screen section and the wn.bgcolor('Navy') line. Create a new turtle element called #Draw border by typing:

wn.bgcolor('Navy') 

# Draw border
mypen = turtle.Turtle()
mypen.penup()
mypen.setposition(-300, -300)
mypen.pendown()
mypen.pensize(3)
mypen.color('white')

for side in range(4):
    mypen.forward(600)
    mypen.left(90)

mypen.hideturtle()

# Create player turtle

setposition places the mypen turtle in the bottom left hand-corner of your screen

pendown gets your mypen turtle ready to draw, and the for side in range (4): tells your mypen turtle to draw four sides using a simple loop: draw forward by 600 points, then turn left, and repeat four times.

Step 3.

Save and Run your module.

Notice how a turtle ‘draws’ the borders when the module loads? If you would like to get straight to the turtle-y action, try setting mypen.speed(0) after setting mypen.color('...')

Now we have to do something called boundary checking, what this will do is check the location of our turtleand if the turtle’s X coordinate is lower than -290 or greater than 290, we have hit either the left or right border (X-axis). Similarly, if the Y coordinate is greater than 290 or lower than -290, we have hit either the top or bottom border (Y-axis). We then simply choose what we want to happen when this occurs - for this game we are going to bounce off the border wall at 180 degrees.

Step 4.

As we need this to happen every time during the game we need the code to be written within the while True loop under the line player.forward\(speed\):

while True:
    player.forward(speed)

    # Boundary Player Checking x coordinate
    if player.xcor() > 290 or player.xcor() < -290:
        player.right(180)

    # Boundary Player Checking y coordinate
    if player.ycor() > 290 or player.ycor() < -290:
        player.right(180)

Step 5.

Save and then Run your module.

Your code should now look like this:

#Turtle Graphics Game
import turtle


#Set up screen
turtle.setup(650,650)
wn = turtle.Screen()
wn.bgcolor("Navy")

#Draw border
mypen = turtle.Turtle()
mypen.penup()
mypen.setposition(-300,-300)
mypen.pendown()
mypen.pensize(3)
for side in range(4):
    mypen.forward(600)
    mypen.left(90)
mypen.hideturtle()

#Create player turtle
player = turtle.Turtle()
player.color("darkorange")
player.shape("turtle")
player.penup()
player.speed(0) 

#Set speed variable
speed = 1

#Define functions

def turn_left():
    player.left(30)

def turn_right():
    player.right(30)

def increase_speed():
    global speed
    speed += 1

#Set keyboard bindings
turtle.listen()
turtle.onkey(turn_left, "Left")
turtle.onkey(turn_right, "Right")
turtle.onkey(increase_speed, "Up") 


while True:
    
    player.forward(speed)

    #Boundary Checking x coordinate
    if player.xcor() > 290 or player.xcor() < -290:
        player.right(180)
    #Boundary Checking y coordinate
    if player.ycor() > 290 or player.ycor() < -290:
        player.right(180)