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Books / Coding Games With Pygame Zero & Python / Chapter 5
Arcade games
In this chapter
Collisions
Arcade games need to know when one Actor sprite has hit another Actor sprite. Most of this code is copied from Program 4.2 and Program 4.5.
WIDTH = 500
HEIGHT = 500
alien = Actor("alien")
alien.pos = (400, 50)
box = Rect((20, 20), (100, 100))
def draw():
screen.clear()
screen.draw.filled_rect(box, "red")
alien.draw()
def update():
if keyboard.right:
alien.x = alien.x + 2
elif keyboard.left:
alien.x = alien.x - 2
box.x = box.x + 2
if box.x > WIDTH:
box.x = 0
if alien.colliderect(box):
print("hit")
Program 5.1 Collisions
Exercise
Add vertical movement (as you did in Exercise Program 4.5).
Advanced
Make the box chase the alien.
Advanced
Print number of times the box hits the alien (i.e. the score).
Chase
Instead of moving constantly to the right we can make the movement conditional with an if statement so the box chases the alien. Most of this code is copied from Program 5.1. New lines are highlighted. We have also changed what happens when the box catches the alien: the program now exits and you must run it again to play again. This may not be what you want in your game!
WIDTH = 500
HEIGHT = 500
alien = Actor("alien")
alien.pos = (400, 50)
box = Rect((20, 20), (100, 100))
def draw():
screen.clear()
screen.draw.filled_rect(box, "red")
alien.draw()
def update():
if keyboard.right:
alien.x = alien.x + 2
elif keyboard.left:
alien.x = alien.x - 2
if box.x < alien.x:
box.x = box.x + 1
if box.x > alien.x:
box.x = box.x - 1
if alien.colliderect(box):
exit()
Program 5.2 Alien chase
Exercise
Add vertical movement (as you did in previous exercise).
Advanced
Draw a new enemy image. Save it as enemy.png in your mu_code/images folder. Load it as an Actor(‘enemy’) instead of the Rect().
Powerup
Instead of an enemy the box here is a powerup that the player must collect. When he does it disappears and moves to a new location.
WIDTH = 500
HEIGHT = 500
import random
alien = Actor("alien")
alien.pos = (400, 50)
box = Rect((20, 20), (100, 100))
score = 0
def draw():
screen.clear()
screen.draw.filled_rect(box, "green")
alien.draw()
def update():
global score
if keyboard.right:
alien.x = alien.x + 2
elif keyboard.left:
alien.x = alien.x - 2
if alien.colliderect(box):
box.x = random.randint(0, WIDTH)
box.y = random.randint(0, HEIGHT)
score = score + 1
print("Score:", score)
Program 5.3 Collect the powerups
Exercise
Add vertical movement.
Sound and animation
Pygame Zero comes with one other image alien_hurt.png and one sound
eep.wav. If you want more you will have to add them to the sounds
and images folders.
Most of this code is copied from Program 5.1
WIDTH = 500
HEIGHT = 500
alien = Actor("alien")
alien.pos = (0, 50)
box = Rect((20, 20), (100, 100))
def draw():
screen.clear()
screen.draw.filled_rect(box, "red")
alien.draw()
def update():
if keyboard.right:
alien.x = alien.x + 2
elif keyboard.left:
alien.x = alien.x - 2
box.x = box.x + 2
if box.x > WIDTH:
box.x = 0
# PLAY SOUND AND SHOW IMAGE WHEN HIT
if alien.colliderect(box):
alien.image = 'alien_hurt'
sounds.eep.play()
else:
alien.image = 'alien'
Program 5.4 Sound and animation upon collision
Exercise
Record your own sound effect and add it to the game.
Advanced
Add more boxes or sprites that move in different ways for the player to avoid.
Advanced
Add a second alien controlled by different keys or gamepad for player 2.
Mouse clicks
This uses a function call-back for event-based input. It is similar to Program 5.4 but:
- The box has been removed.
- There is an
on_mouse_down()special function that is called automatically when the player click the mouse. - The score is displayed.
alien = Actor("alien")
alien.pos = (0, 50)
score = 0
def draw():
screen.clear()
alien.draw()
screen.draw.text("Score "+str(score), (0,0))
def update():
if keyboard.right:
alien.x = alien.x + 2
elif keyboard.left:
alien.x = alien.x - 2
alien.image = 'alien'
def on_mouse_down(pos, button):
global score
if button == mouse.LEFT and alien.collidepoint(pos):
alien.image = 'alien_hurt'
sounds.eep.play()
score = score + 1
Program 5.5 Getting input from mouse clicks
Mouse movement
# wiggle your mouse around the screen!
alien = Actor("alien")
def draw():
screen.clear()
alien.draw()
def on_mouse_move(pos):
alien.pos = pos
Program 5.6 Getting input from mouse movement
Exercise
What happens if you delete line 8 and replace it with this:
animate(alien, pos=pos, duration=1, tween='bounce_end')
Exercise
What happens if you change on_mouse_move to on_mouse_down?
Advanced
Make a game with one alien controlled by mouse and another controlled by keyboard