Have Enemies Periodically Shoot#
Having enemies shoot every x seconds is a bit more complex than shooting randomly as shown in Have Enemies Randomly Shoot. This is because we need to track how often we shoot, and how long it has been since we last shot.
This example uses custom sub-class EnemySprite. The extra attributes allow
us to track the periodic timing. See the highlighted lines for what is specific
to this example.
sprite_bullets_periodic.py#
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Show how to have enemies shoot bullets at regular intervals.
If Python and Arcade are installed, this example can be run from the command line with:
python -m arcade.examples.sprite_bullets_periodic
"""
import arcade
SCREEN_WIDTH = 800
SCREEN_HEIGHT = 600
SCREEN_TITLE = "Sprites and Periodic Bullets Example"
class EnemySprite(arcade.Sprite):
""" Enemy ship class that tracks how long it has been since firing. """
def __init__(self, image_file, scale, bullet_list, time_between_firing):
""" Set up the enemy """
super().__init__(image_file, scale)
# How long has it been since we last fired?
self.time_since_last_firing = 0.0
# How often do we fire?
self.time_between_firing = time_between_firing
# When we fire, what list tracks the bullets?
self.bullet_list = bullet_list
def on_update(self, delta_time: float = 1 / 60):
""" Update this sprite. """
# Track time since we last fired
self.time_since_last_firing += delta_time
# If we are past the firing time, then fire
if self.time_since_last_firing >= self.time_between_firing:
# Reset timer
self.time_since_last_firing = 0
# Fire the bullet
bullet = arcade.Sprite(":resources:images/space_shooter/laserBlue01.png")
bullet.center_x = self.center_x
bullet.angle = -90
bullet.top = self.bottom
bullet.change_y = -2
self.bullet_list.append(bullet)
class MyGame(arcade.Window):
""" Main application class """
def __init__(self):
super().__init__(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_TITLE)
arcade.set_background_color(arcade.color.BLACK)
self.player = None
self.player_list = None
self.enemy_list = None
self.bullet_list = None
def setup(self):
""" Setup the variables for the game. """
self.player_list = arcade.SpriteList()
self.enemy_list = arcade.SpriteList()
self.bullet_list = arcade.SpriteList()
# Add player ship
self.player = arcade.Sprite(":resources:images/space_shooter/playerShip1_orange.png", 0.5)
self.player_list.append(self.player)
# Add top-left enemy ship
enemy = EnemySprite(":resources:images/space_shooter/playerShip1_green.png",
scale=0.5,
bullet_list=self.bullet_list,
time_between_firing=2.0)
enemy.center_x = 120
enemy.center_y = SCREEN_HEIGHT - enemy.height
enemy.angle = 180
self.enemy_list.append(enemy)
# Add top-right enemy ship
enemy = EnemySprite(":resources:images/space_shooter/playerShip1_green.png",
scale=0.5,
bullet_list=self.bullet_list,
time_between_firing=1.0)
enemy.center_x = SCREEN_WIDTH - 120
enemy.center_y = SCREEN_HEIGHT - enemy.height
enemy.angle = 180
self.enemy_list.append(enemy)
def on_draw(self):
"""Render the screen. """
self.clear()
self.enemy_list.draw()
self.bullet_list.draw()
self.player_list.draw()
def on_update(self, delta_time):
""" All the logic to move, and the game logic goes here. """
# Call on_update for each enemy in the list
self.enemy_list.on_update(delta_time)
# Get rid of the bullet when it flies off-screen
for bullet in self.bullet_list:
if bullet.top < 0:
bullet.remove_from_sprite_lists()
self.bullet_list.update()
def on_mouse_motion(self, x, y, delta_x, delta_y):
"""
Called whenever the mouse moves.
"""
self.player.center_x = x
self.player.center_y = 20
def main():
""" Run the game """
window = MyGame()
window.setup()
arcade.run()
if __name__ == "__main__":
main()
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