Unit 12.3A · Term 3

Full Game Project: "Catch the Data"

It's time to bring it all together! We will build a complete game called "Catch the Data" where the player moves a basket to catch falling data packets while avoiding viruses.

Learning Objectives

12.5.3.9 Create a simple computer game

Lesson Presentation

12.3A-full-game.pdf · Slides for classroom use

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Game Design

The Blueprint

Player: Only moves left/right at the bottom.
Packets (Green): Fall from top. +10 Score.
Viruses (Red): Fall from top. Game Over if hit.
Win Condition: Reach 500 points.
Lose Condition: Hit a virus.

Complete Code

Copy this code into a new file catch_the_data.py and run it.

import pygame
import sys
import random

# --- Constants ---
WIDTH, HEIGHT = 800, 600
FPS = 60
WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
GREEN = (0, 200, 100)
RED = (200, 50, 50)
BLUE = (50, 100, 255)

# --- Classes ---
class Player(pygame.sprite.Sprite):
    def __init__(self):
        super().__init__()
        self.image = pygame.Surface((60, 40))
        self.image.fill(BLUE)
        self.rect = self.image.get_rect(center=(WIDTH//2, HEIGHT - 50))
        self.speed = 8

    def update(self):
        keys = pygame.key.get_pressed()
        if keys[pygame.K_LEFT]:
            self.rect.x -= self.speed
        if keys[pygame.K_RIGHT]:
            self.rect.x += self.speed
        
        # Keep on screen
        self.rect.clamp_ip(pygame.Rect(0, 0, WIDTH, HEIGHT))

class FallingObject(pygame.sprite.Sprite):
    def __init__(self, obj_type):
        super().__init__()
        self.type = obj_type 
        size = 30 if obj_type == "packet" else 40
        self.image = pygame.Surface((size, size))
        
        if self.type == "packet":
            self.image.fill(GREEN)
            self.speed = random.randint(4, 7)
        else:
            self.image.fill(RED)
            self.speed = random.randint(6, 9)
            
        self.rect = self.image.get_rect(
            center=(random.randint(20, WIDTH-20), -20)
        )

    def update(self):
        self.rect.y += self.speed
        if self.rect.top > HEIGHT:
            self.kill()

# --- Setup ---
pygame.init()
screen = pygame.display.set_mode((WIDTH, HEIGHT))
pygame.display.set_caption("Catch the Data!")
clock = pygame.time.Clock()
font = pygame.font.SysFont("Arial", 28)
big_font = pygame.font.SysFont("Arial", 72)

# Game State
player = Player()
all_sprites = pygame.sprite.Group(player)
packets = pygame.sprite.Group()
viruses = pygame.sprite.Group()

score = 0
game_state = "playing" # playing, won, lost

# Timer for spawning
SPAWN_EVENT = pygame.USEREVENT + 1
pygame.time.set_timer(SPAWN_EVENT, 500) # Every 500ms

# --- Main Loop ---
running = True
while running:
    # 1. Event Handling
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
            
        if game_state == "playing":
            if event.type == SPAWN_EVENT:
                # 80% chance for packet, 20% for virus
                if random.random() < 0.8:
                    obj = FallingObject("packet")
                    packets.add(obj)
                    all_sprites.add(obj)
                else:
                    obj = FallingObject("virus")
                    viruses.add(obj)
                    all_sprites.add(obj)
        
        # Restart logic
        if game_state != "playing" and event.type == pygame.KEYDOWN:
            if event.key == pygame.K_r:
                # Reset game
                game_state = "playing"
                score = 0
                all_sprites.empty()
                packets.empty()
                viruses.empty()
                player = Player()
                all_sprites.add(player)

    # 2. Update
    if game_state == "playing":
        all_sprites.update()
        
        # Check collisions
        # Packet hits
        hits = pygame.sprite.spritecollide(player, packets, True)
        if hits:
            score += 10 * len(hits)
            
        # Virus hits
        hits = pygame.sprite.spritecollide(player, viruses, False)
        if hits:
            game_state = "lost"
            
        # Win condition
        if score >= 500:
            game_state = "won"

    # 3. Render
    screen.fill(BLACK)
    
    if game_state == "playing":
        all_sprites.draw(screen)
        
        # Draw UI
        score_text = font.render(f"Data: {score}/500", True, WHITE)
        screen.blit(score_text, (10, 10))
        
    elif game_state == "lost":
        text = big_font.render("SYSTEM INFECTED!", True, RED)
        rect = text.get_rect(center=(WIDTH//2, HEIGHT//2))
        screen.blit(text, rect)
        
        sub = font.render("Press R to Reboot", True, WHITE)
        sub_rect = sub.get_rect(center=(WIDTH//2, HEIGHT//2 + 60))
        screen.blit(sub, sub_rect)
        
    elif game_state == "won":
        text = big_font.render("UPLOAD COMPLETE!", True, GREEN)
        rect = text.get_rect(center=(WIDTH//2, HEIGHT//2))
        screen.blit(text, rect)
        
        sub = font.render(f"Final Score: {score}. Press R to Play Again", True, WHITE)
        sub_rect = sub.get_rect(center=(WIDTH//2, HEIGHT//2 + 60))
        screen.blit(sub, sub_rect)

    pygame.display.flip()
    clock.tick(FPS)

pygame.quit()
sys.exit()

Code Breakdown

1. Game States

We use a variable game_state separate logic for playing, winning, and losing. When the game ends, we stop updating sprites and stop spawning items, but keep the loop running to show the "Game Over" text and wait for a restart key.

2. Timers (USEREVENT)

Instead of relying on random chance every frame (which varies with FPS), we use pygame.time.set_timer() to trigger a customer event exactly every 500 milliseconds. This makes spawning consistent.

3. Inheritance

Use a single FallingObject class for both packets and viruses. We pass a type argument to __init__ to decide if it's green (good) or red (bad). This saves writing two nearly identical classes.

Project Extensions

Apply

Add a "Golden Packet" that spawns rarely gives +50 points and plays a sound.

Create

Add difficulty scaling: Make objects fall faster as the score gets higher.

Create

Add lives: Allow the player to hit 3 viruses before Game Over. Display lives as icons.