class Alien(Entity):
spr_alien = 'assets/alien.png'
snd_alien_die = 'assets/explosion-alien.wav'
def __init__(self, x, y):
super().__init__(x, y)
def added(self):
# Slightly slower than the player
self.speed = 200
self.width = 36
self.height = 32
self.graphic = Image(Alien.spr_alien)
self.type = 'alien'
self.alien_die = Sfx(Alien.snd_alien_die)
def update(self):
# Constantly move to the left
self.x -= self.speed * PP.elapsed
# Just a bit of math to make them do pretty waves as
# they come across the screen
self.y += (math.cos(self.x / 50) * 50) * PP.elapsed
# Destoy it if it does offscreen.
if self.x < -40:
self.destroy()
# If it's collided with a bullet, remove both, and increase the score.
bullet = self.collide('bullet', self.x, self.y)
if bullet:
self.world.hud.score += 1
bullet.destroy()
self.destroy()
self.alien_die.play()
def destroy(self):
self.world.remove(self)
class Ship(Entity):
# Paths to resources.
spr_ship = 'assets/ship.png'
snd_ship_die = 'assets/explosion-ship.wav'
snd_bullet_shoot = 'assets/bullet.wav'
def added(self):
# Keeping track of how fast it should be able to move, in this case,
# 250 units (pixels per second)
self.speed = 250
# Set the initial location of the sprite
self.x = self.y = 50
# Set the graphic to render onto screen to a new Image instance.
self.graphic = Image(Ship.spr_ship)
# Width and Height are primarily used for collision detection.
# should be indicative of the size of the sprite (in most cases.)
self.width = 40
self.height = 16
# The type of an entity is an arbitrary string that categorises what it is
# Types are used for several things, most predominantly collision checking,
# where you can specify a type, which then will restrict collisions detected
# to Entities of that type.
self.type = 'ship'
# Some sound resources to sound cool with
self.ship_die = Sfx(Ship.snd_ship_die)
self.bullet_shoot = Sfx(Ship.snd_bullet_shoot)
# I've delegated the update code into a few smaller functions to make
# it more readable.
def update(self):
self.move()
self.constrain()
self.shoot()
self.collision()
# Check if the keys are being pressed, and if they are, move in the appropriate
# direction. The self.speed * PP.elapsed is used to make sure the object moves at
# a steady rate, rather than something that will change depending on the FPS
def move(self):
if Input.check(Key.RIGHT):
self.x += self.speed * PP.elapsed
if Input.check(Key.LEFT):
self.x -= self.speed * PP.elapsed
if Input.check(Key.DOWN):
self.y += self.speed * PP.elapsed
if Input.check(Key.UP):
self.y -= self.speed * PP.elapsed
# Make sure the ship doesn't go off-screen.
def constrain(self):
self.clamp_horizontal(16, PP.screen.width - 16)
self.clamp_vertical(16, PP.screen.height - 16)
# If the user pressed space, create a new bullet instance, add it to the world,
# and play a cool sound effect
def shoot(self):
if Input.pressed(Key.SPACE):
self.world.add(Bullet(self.x + 36, self.y + 12))
self.bullet_shoot.play()
# Check to see if we have collided with an alien (notice usage of type to
# filter collision check). If we have collided, it's game over, play the
# appropriated SFX to imply as such.
def collision(self):
alien = self.collide('alien', self.x, self.y)
if alien:
alien.destroy()
self.destroy()
self.ship_die.play()
self.world.hud.game_over()
# Removes the entity from the world.
def destroy(self):
self.world.remove(self)