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Introduction to Pygame

Course: Year 11 Digital Technologies
Year Level: Level 6 / Year 11
Unit / Module: 01 Programming Foundations
Aligned Standard(s): AS92004
Lesson Context: core concept / application
Estimated Time: 50 minutes

1. Purpose of These Notes​

Purpose of These Notes — what they do, what they are not, and connection to AS92004

These notes exist to:

  • explain what Pygame is and how it connects to the Python you already know
  • show how the programming fundamentals (IPO, variables, selection, iteration) appear inside a game
  • give you the vocabulary to describe what your game code is doing and why
  • prepare you to build and explain a Pygame project for AS92004

These notes are not a tutorial you copy line by line. They explain the ideas behind Pygame so you can make and justify your own decisions.

2. Key Concepts (Overview)​

Key Concepts overview — six core ideas connecting Pygame to Python fundamentals

  • A Pygame program is still a Python program — variables, selection, iteration, and functions all apply.
  • Every Pygame program follows a game loop: handle events → update state → draw the screen.
  • Events are how the program receives input (keyboard, mouse, window close).
  • Surfaces are where things are drawn; the display surface is what the player sees.
  • The game loop is an example of iteration running continuously until the player quits.
  • Game state is stored in variables and changed using selection and assignment.

If you cannot explain the game loop and how your code handles input, updates state, and draws output, you have not understood the topic.

Key Video: The Ultimate Introduction to Pygame​

This video provides a comprehensive overview of how video games work conceptually and how Pygame facilitates the game loop and event handling. The ultimate introduction to Pygame

3. Core Explanation​

What Is Pygame?​

What Pygame provides versus what you still write

Pygame is a Python library for making 2D games and interactive programs. It handles drawing to the screen, reading keyboard and mouse input, and keeping time — things that plain Python cannot do by itself.

Pygame does not change how Python works. You still use variables, functions, conditions, and loops. Pygame just gives you new tools to work with.

Why Use Pygame for AS92004?​

AS92004 assesses whether you can develop a computer program and explain how and why it works. A Pygame project lets you demonstrate:

  • variables (player position, score, health, speed)
  • selection (checking collisions, choosing what happens when a key is pressed)
  • iteration (the game loop itself, and any repeating game logic)
  • testing and debugging (does the player move correctly? do edge cases break anything?)

The game is the context. The programming fundamentals are the evidence.

The Game Loop​

The Game Loop — three phases mapped to IPO

The most important idea in Pygame is the game loop. Every game runs a loop that repeats many times per second. Each time through the loop, three things happen:

  1. Handle events — check what the player did (pressed a key, clicked, closed the window)
  2. Update state — change variables based on what happened (move the player, add to score, reduce health)
  3. Draw — clear the screen and redraw everything in its new position

This is the Input–Process–Output (IPO) model applied continuously:

IPO StageGame Loop StepExample
InputHandle eventsPlayer presses the right arrow key
ProcessUpdate statePlayer x-position increases by 5
OutputDrawPlayer rectangle drawn at new position

The loop repeats until a quit event is detected.

Key Video: Pygame in 90 Minutes​

This video walks through the implementation of a basic game loop, handling the QUIT event, and the fundamentals of drawing to the screen. Pygame in 90 Minutes - For Beginners

Events​

Events — how games receive and handle input using selection

An event is something that happens — a key press, a mouse click, or the player closing the window. Pygame collects events into a queue. Each time through the loop, you check the queue and decide what to do.

This is selection: if the event is a quit event, stop the loop. If the event is a key press, change a variable.

Surfaces and Drawing​

Surfaces and Drawing — Clear, Draw, Flip workflow

A surface is a rectangular area of pixels. The display surface is the game window. You draw shapes, images, and text onto surfaces.

Drawing in Pygame works like a flipbook:

  1. Clear the screen (fill it with a background colour)
  2. Draw everything in its current position
  3. Flip the display (show the new frame)

If you skip the clear step, old drawings stay on the screen and the game looks broken. This is a common mistake.

Coordinates and Positioning​

Pygame coordinate system — (0,0) at top-left, y increases downward

Pygame uses a coordinate system where:

  • (0, 0) is the top-left corner of the window
  • x increases to the right
  • y increases downward (not upward like in maths)

This catches many students. If you increase a y-value, the object moves down.

Controlling Speed​

Controlling Speed — with and without a clock

Pygame uses a clock to control how fast the game loop runs. Setting the clock to 60 frames per second means the loop runs 60 times each second. This keeps the game smooth and consistent.

Without a clock, the loop runs as fast as the computer allows, which makes the game behave differently on different machines.

4. Diagrams and Visual Models​

The Game Loop​

IPO Model in Pygame​

Pygame Tutorial for Beginners: Space Invaders Project​

This video applies the IPO model and coordinates to build a classic Space Invaders game, focusing on player positioning and movement logic. Pygame Tutorial for Beginners - Python Game Development Course

Pygame Coordinate System​

Pygame Program Structure​

5. Worked Examples (Conceptual, Not Procedural)​

Worked Example 1: Understanding the Game Loop​

Worked Example: Moving Square — variables, each frame, and the clear-step bug

Consider a game where a square moves right when the player presses the right arrow key.

What variables are needed?

  • player_x — the x-position of the square
  • player_y — the y-position of the square
  • speed — how many pixels to move per frame

What happens in the loop?

  1. Handle events: Selection checks the event queue for pygame.KEYDOWN. If the key is the right arrow, set a movement flag to True.
  2. Update state: Selection checks the movement flag. If True, player_x increases by speed.
  3. Draw: Clear the screen. Draw the square at (player_x, player_y). Flip the display.

6. Glossary of Terms​

  • Event: anything that happens during the game (key press, mouse click, window close)
  • Event queue: the list of events Pygame has collected since the last check
  • Surface: a rectangular area of pixels; the display surface is the game window
  • Blit: drawing one surface onto another
  • Flip / Update: showing the newly drawn frame on screen
  • Frame: one complete cycle of the game loop; one image shown to the player
  • FPS (frames per second): how many frames are drawn each second; controls game speed
  • Clock: a Pygame object that controls the frame rate
  • Rect: a rectangle object used for positioning and collision detection
  • Sprite: a game object (player, enemy, item) represented visually on screen
  • Collision detection: checking whether two game objects overlap
  • Game state: the current values of all variables that describe what is happening in the game

Students are expected to use this vocabulary accurately when explaining their work.

Looking Ahead​

The concepts in this topic connect directly to your AS92004 project:

  • the game loop gives you the structure for your program
  • events give you input handling
  • variables and selection give you game logic
  • testing and debugging ensure your game works as intended

You will spend the next several lessons building a Pygame project. The programming fundamentals you learned earlier — IPO, variables, selection, iteration, testing — are the tools you will use every day.