Getting Started

You will need to have pygame installed. (JIS Rooms R0D and R1J only)
Test by typing ‘import pygame’ into the idle prompt with no error

>>>import pygame
>>>>

If you get an error its not installed

History / Background

• Pong was the first commercially available Computer game released in November 1972
• Pong was maybe copied from Electronic Tennis or Magnavox Odyssey’s Tennis game
• Electronic Tennis was programmed some time in the early 1960’s but never released as a product
• Magnavox Odyssey was the world’s first ever video console – Released in August 1972

Youtube link

In Cabinet Format

Magnavox Odyssey (1972)

World’ First Video Console

Pygame Setup

# Note: if using MU run in Python3 mode not pygame zero mode
import pygame
screen = pygame.display.set_mode((300, 300))

#set up initial values for the x and y coordinates
x = 0 
y = 0 
radius = 10
red = 255,0,0

pygame.draw.circle(screen, red, (x,y),radius)  #puts the circle into the graphics memory
pygame.display.update()                        #draws the circle on the screen

#to ensure graceful exit
anyinput = input("press enter to quit") #note the input must be in the python window - not pygame window
pygame.quit()

Rect

Drawing a rectangle is a bit weird. As a rect object must be inside the draw statement.

 pygame.draw.rect(screen, blue, pygame.Rect(0,0,rectwidth,rectheight) ) 

Reference

pygame.draw.rect(Surface, color, Rect, width=0) -> Rect

pygame.Rect(left, top, width, height) -> Rect

Drawing Practice

Produce code for the following images and copy and paste the answers into the boxes.

• You should use variables for screen height and screen width.
• Orange is red with more than a half green
• Think about the sequence of your instructions to get the circle on top of the background colour

1. 
   300×300
   

2. 
   300×300
   

3. 
   75×75
   

4. 
   200×200
   

5. 
   200×200
   

6. 
   200×200 How are you going to repeat all those circles?
   

Move the ball

Increment x (speed) within a loop to move the ball

x = x + 5
pygame.draw.circle(screen, red, (x,y),radius)
pygame.display.update()

Extension (optional)

Use variable dx as the difference in the x coordinate between old and new position

dx  = 5 # This stays outside the loop

x = x + dx 

What is the advantage of using dx?

Screen Refresh

To give the idea of movement we need to

• draw the ball
• wait
• clear the old ball before we draw the new one

Waiting in python

import time  #do this in the first line or 2 of your code

time.sleep(0.01)  #asks the computer to wait

Add the main Loop

We increment the x variable to increase it each time the loop is used. Here is the psuedocode.
Notice the 5 steps inside the loop

loop (forever)
    # 1. draw the circle
    # 2. update the screen
    # 3. wait a bit
    # 4. draw over the circle with background colour
    # 5. increment x to the new position
endloop

Real Games programming

There are better more efficient ways to move the ball, but this is the simplest.

Bounce – “If” Statement

When the ball gets to the edge of the screen we need it to bounce back

if x > 300 then:
  dx = ??? # you need to think about this   

Extension

use boolean OR to add the bounce to the left wall

OR in python must be in lower case ie or

Y Up and Down

Can you add up and down movement?

• Initialise the variable y
• Increment y
• Bounce if it hits the bottom wall (OR the top)

Score a Point

The loop could stop when the ball goes past the left edge of the screen. You will need to change you bounce condition for scoring

• Initialise (Create) a variable “Score” that starts at zero
• increment the score each time the ball passes to the left of the screen
• Print the score (see below).

.

GraphicsWindow.DrawText(100,0, Score)

Then you can add an new loop to keep playing points until the score reaches 3

While (Score < 3)
  '..Main Loop and some variable initialization goes here
EndWhile

Controls – Event Handling

Create The Bat

Use a rectangle from the coordinate bat_y for the y coordinate for the bat. The bat can extend down 40 pixels

import pygame
import sys #This is needed for the sys.exit() which can stop pygame crashing on exit.
#The following code must be included inside your main loop (at the bottom is best) 
  #be careful with your indentations!!
    for event in pygame.event.get():
        print(event) #optional - will print to the text window not the pygame window
        if event.type == pygame.KEYDOWN:
        #using Arrow keys
            if event.key == pygame.K_RIGHT:
                dx = 1
                dy = 0
            if event.key == pygame.K_LEFT:
                dx = -1
                dy = 0
            if event.key == pygame.K_UP:
                dy = -1
                dx = 0
            if event.key == pygame.K_DOWN:
                dy = 1
                dx = 0
            #using wasd keys (only partially completed)
            if event.key == pygame.K_d:
                dx = 1
                dy = 0
            if event.key == pygame.K_a:
                dx = -1
                dy = 0
        #or use the mouse 
        if event.type == pygame.MOUSEMOTION:
            (notused, y) = event.pos
            x = 0            
        if event.type == pygame.QUIT:   #
            pygame.quit()
            sys.exit()

Collision detection (Bat and Ball)

You will need to have a number of conditions occuring at once. You need to nest your “if” statements as below:

  if (cond 1):
    if (cond 2): 
      if (cond 3):
         #bounce

Or alternatively this might work

  if (cond 1) or (cond 2) or (cond 3):
      #bounce    

Finish the Game

You could try

• 1 or 2 Player?
• Tennis or Squash?
• Be able to direct the ball using different parts of the paddle
• Some random bounce using Math.GetRandomNumber(10)
• Colour
• Instruction Screens
• Levels with faster speeds
• Variations eg. 2 way with gravity Pong (Needs IE with Silverlight installed)
• An alternative method using Shapes.Move(ball, x, y) where ball = Shapes.AddEllipse(16, 16) This avoids the need to do a screen refresh.