Unit 12.2A · Term 2

Mouse Control

PyGame tracks the mouse position, button clicks, and movement through events and the pygame.mouse module — essential for interactive games and user interfaces.

Learning Objectives

12.5.3.3 Code mouse control

Lesson Presentation

12.2A-mouse-control.pdf · Slides for classroom use

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Conceptual Anchor

The Touch Screen Analogy

Just like a touch screen knows where your finger is and when you tap, PyGame tracks the mouse cursor's coordinates and detects clicks. You can use this to let players aim, click buttons, drag objects, and more.

Rules & Theory

Mouse Functions

Function	Returns	Example
`pygame.mouse.get_pos()`	(x, y) tuple — cursor position	`mx, my = pygame.mouse.get_pos()`
`pygame.mouse.get_pressed()`	(left, middle, right) — booleans	`buttons = pygame.mouse.get_pressed()`
`pygame.mouse.set_visible(bool)`	Show/hide cursor	`pygame.mouse.set_visible(False)`
`pygame.mouse.set_pos((x,y))`	Move cursor to position	`pygame.mouse.set_pos((400, 300))`

Mouse Events

Event	When It Fires	Attributes
`MOUSEBUTTONDOWN`	Button pressed	`event.pos`, `event.button`
`MOUSEBUTTONUP`	Button released	`event.pos`, `event.button`
`MOUSEMOTION`	Cursor moved	`event.pos`, `event.rel`

Button Numbers

event.button: 1 = left, 2 = middle, 3 = right, 4 = scroll up, 5 = scroll down.

Worked Examples

1 Object Follows Mouse

import pygame, sys

pygame.init()
screen = pygame.display.set_mode((800, 600))
pygame.display.set_caption("Mouse Follower")
clock = pygame.time.Clock()

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    # Get mouse position
    mx, my = pygame.mouse.get_pos()

    screen.fill((30, 30, 30))

    # Draw circle at mouse position
    pygame.draw.circle(screen, (0, 200, 255), (mx, my), 25)

    # Show coordinates
    font = pygame.font.SysFont("Arial", 18)
    text = font.render(f"({mx}, {my})", True, (255, 255, 255))
    screen.blit(text, (mx + 30, my - 10))

    pygame.display.flip()
    clock.tick(60)

pygame.quit()
sys.exit()

2 Click to Paint Dots

import pygame, sys

pygame.init()
screen = pygame.display.set_mode((800, 600))
pygame.display.set_caption("Click Painter")
clock = pygame.time.Clock()

dots = []  # store painted dots

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        if event.type == pygame.MOUSEBUTTONDOWN:
            if event.button == 1:  # left click
                dots.append(event.pos)

    screen.fill((255, 255, 255))
    for dot in dots:
        pygame.draw.circle(screen, (255, 50, 50), dot, 15)

    pygame.display.flip()
    clock.tick(60)

pygame.quit()
sys.exit()

3 Clickable Button

import pygame, sys

pygame.init()
screen = pygame.display.set_mode((800, 600))
pygame.display.set_caption("Button Demo")
clock = pygame.time.Clock()
font = pygame.font.SysFont("Arial", 28)

# Button rect
button = pygame.Rect(300, 250, 200, 60)
clicks = 0

running = True
while running:
    mx, my = pygame.mouse.get_pos()

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        if event.type == pygame.MOUSEBUTTONDOWN:
            if button.collidepoint(mx, my):  # click on button?
                clicks += 1

    screen.fill((30, 30, 30))

    # Change color on hover
    if button.collidepoint(mx, my):
        color = (80, 180, 80)  # green hover
    else:
        color = (60, 120, 60)

    pygame.draw.rect(screen, color, button, border_radius=8)
    label = font.render(f"Clicks: {clicks}", True, (255, 255, 255))
    screen.blit(label, (button.x + 30, button.y + 15))

    pygame.display.flip()
    clock.tick(60)

pygame.quit()
sys.exit()

Common Pitfalls

get_pressed() vs MOUSEBUTTONDOWN Event

get_pressed() returns the current state (held down?). MOUSEBUTTONDOWN fires once per click. For single-click actions (buttons), use the event. For continuous actions (dragging), use get_pressed().

Tasks

Apply

Create a drawing app: hold left mouse button to draw a line trail as the mouse moves.

Apply

Create a "target practice" game: random circles appear, click them to score points.

Create

Build a color picker: 5 colored squares at the top, click one to select the paint color, then draw with that color.

Self-Check Quiz

Q1: How do you get the current mouse position?

mx, my = pygame.mouse.get_pos() — returns (x, y) tuple.

Q2: How do you detect if a button was clicked?

Use button_rect.collidepoint(mx, my) inside a MOUSEBUTTONDOWN event to check if the click position is inside the button rectangle.

Q3: What button number is left click?

event.button == 1 — 1=left, 2=middle, 3=right.