Teach Your Kids To Code: A Parent-friendly Guide to Python Programming

190 Chapter 8

SmileyMove.py

import pygame # Setup

pygame.init()

screen = pygame.display.set_mode([600,600])

keep_going = True

pic = pygame.image.load("CrazySmile.bmp")

colorkey = pic.get_at((0,0))

pic.set_colorkey(colorkey)

picx = 0

picy = 0

BLACK = (0,0,0)

timer = pygame.time.Clock() # Timer for animation

while keep_going: # Game loop

for event in pygame.event.get():

if event.type == pygame.QUIT:

keep_going = False

picx += 1 # Move the picture

picy += 1

screen.fill(BLACK) # Clear screen

screen.blit(pic, (picx,picy))

pygame.display.update()

timer.tick(60) # Limit to 60 frames per second

pygame.quit() # Exit

The remaining problem is that the smiley still goes all the way

off the screen in a few seconds. That’s not very entertaining. Let’s

change our program to keep the smiley face on the screen, bounc-

ing from corner to corner.

Bouncing a Smiley Off a Wall

We’ve added motion from one frame to the next by changing the

position of the image we were drawing on each pass through our

game loop. We saw how to regulate the speed of that animation

by adding a Clock object and telling it how many times per second

to tick(). In this section, we’ll see how to keep our smiley on the

screen. The effect will look a bit like Figure 8-6, with the smiley

appearing to bounce back and forth between two corners of the

drawing window.