Python Arcade – Adding Enemies

In this article, we will learn How we can add enemies in arcade.

Adding Enemies

To add enemy to our game we are going to follow the below steps:

• First, we will create a variable to store the enemy sprite.

Syntax:

 self.enemy = None

• After that, we will create one more variable to store the velocity of the enemy.

Syntax:

self.enemy_move = velocity

• Store our enemy sprite in the enemy variable.

Syntax:

self.enemy = arcade.Sprite("path",1)

• Set the initial coordinates.

Syntax:

self.enemy.center_x = value
self.enemy.center_y = value

• Add the enemy sprite in the scene.

Syntax:

self.scene.add_sprite("Enemy", self.enemy)

• Move the enemy by changing the x coordinate.

Syntax:

self.enemy.center_x += self.enemy_move

• Check for collisions between the player and enemy.

Syntax:

enemy_collide = arcade.check_for_collision_with_list(

            self.player_sprite, self.scene.get_sprite_list(“Enemy”)

        )

• If they are colliding then remove the player sprite.

Syntax:

for enemy in enemy_collide:

      self.player_sprite.remove_from_sprite_lists()

Functions Used:

• draw_text(): This function is used to draw text to the screen using Pyglet’s label.

Syntax: arcade.draw_text(text, x, y, color, size, width, align, font_name)

Parameters:

text: Text we want to display

x : x coordinate

y : y coordinate

color : color of the text

size : Size of the font

width : Width of the text

align : Alignment of the text

font_name : Name of the font

• Camera(): The Camera class is used for controlling the visible viewport.

Syntax: arcade.Camera( width , height, window)

Parameters:

width: width of the viewport

height: height of the viewport

window: Window to associate with this camera

• Scene(): A class that represents a scene object.

Syntax: arcade.Scene(sprite_lists , name_mapping)

Parameters:

sprite_lists: A list of SpriteList objects

name_mapping: A dictionary of SpriteList objects

• PhysicsEnginePlatformer(): Simplistic physics engine, used for platform.

Syntax: arcade.PhysicsEnginePlatformer( player_sprite , platforms, gravity, ladders)

Parameters:

player_sprite: sprite of the player

platforms: The sprites it can’t move through

gravity: Downward acceleration per frame

ladders: Ladders the user can climb on

Sprites Used:

PLATFORM

PLAYER

ENEMY

In the below example, we are going to create a MainGame() class. Inside this class first, we are going to initialize some variables for velocity, camera, score, level, enemy, enemy sprite, and player’s sprite then we will create 6 functions inside this class.

• on_draw(): Inside this function, we will use our camera and draw the scene and our score text on the screen.
• setup(): In this function, we will initialize our camera and scene object then we will load our player and platform’s sprites then we will load our enemy sprite and initialize the starting x and y coordinate. After that, we will call the PhysicsEnginePlatformer() function.
• on_update(): In this function, we will update the x coordinates of the player’s sprite, camera, and physics engine. We will also add our enemy_move variable in the x coordinates of the enemy sprite. Then we will check the collision between the enemy and the player. And if the player is colliding with the enemy then we will remove the player sprite.
• on_key_press() and on_key_release(): In this function, we will change the value of the velocity variable according to the keyboard key that is pressed or released.
• camera_move(): In this function, we will move our camera according to our player’s current position.

Example: Adding enemy

Python3

# Importing arcade module
import arcade

# Creating MainGame class
class MainGame(arcade.Window):
    def __init__(self):
        super().__init__(600, 600,
                         title="Player Movement")

        # Initializing a variable to store
        # the velocity of the player
        self.vel_x = 0

        # Creating variable for Camera
        self.camera = None

        # Creating variable to store current score
        self.score = 0

        # Creating variable to move the enemy
        self.enemy_move = 5

        # Creating variable for enemy sprite
        self.enemy = None

        # Creating scene object
        self.scene = None

        # Creating variable to store player sprite
        self.player = None

        # Creating variable for our game engine
        self.physics_engine = None

    # Creating on_draw() function to draw on the screen
    def on_draw(self):
        arcade.start_render()

        # Drawing the text
        arcade.draw_text('Score :- '+str(self.score),
                         self.player_sprite.center_x - 500 / 2,
                         self.player_sprite.center_y + 200,
                         arcade.color.WHITE, 30, 5000, 'left')

        # Using the camera
        self.camera.use()

        # Drawing our scene
        self.scene.draw()

    def setup(self):
         # Initialize Scene object
        self.scene = arcade.Scene()

        # Using Camera() function
        self.camera = arcade.Camera(600, 600)

        # Loading enemy sprite
        self.enemy = arcade.Sprite("Enemy.png", 1)

        # Initializing the starting coordinates
        self.enemy.center_x = 500
        self.enemy.center_y = 110

        # Adding the enemy sprite in the scene
        self.scene.add_sprite("Enemy", self.enemy)

        # Creating different sprite lists
        self.scene.add_sprite_list("Player")
        self.scene.add_sprite_list("Platforms",
                                   use_spatial_hash=True)

        # Adding player sprite
        self.player_sprite = arcade.Sprite("Player.png", 1)

        # Adding coordinates for the center of the sprite
        self.player_sprite.center_x = 64
        self.player_sprite.center_y = 90

        # Adding Sprite in our scene
        self.scene.add_sprite("Player", self.player_sprite)

        # Adding platform sprite according to level
        platform = arcade.Sprite(f"Platform.png", 1)

        # Adding coordinates for the center of the platform
        platform.center_x = 300
        platform.center_y = 32
        self.scene.add_sprite("Platforms", platform)

        # Creating Physics engine
        self.physics_engine = arcade.PhysicsEnginePlatformer(
            self.player_sprite, self.scene.get_sprite_list("Platforms"), 0.5
        )

    # Creating on_update function to
    # update the x coordinate
    def on_update(self, delta_time):

        # Moving the position of enemy
        self.enemy.center_x += self.enemy_move

        # Changing the direction of enemy movement
        if self.enemy.center_x > 500 or self.enemy.center_x < 160:
            self.enemy_move *= -1

        # Checking if the enemy is colliding with player or not
        enemy_collide = arcade.check_for_collision_with_list(
            self.player_sprite, self.scene.get_sprite_list("Enemy")
        )

        # Looping through each enemy and removing the player
        # if colliding
        for enemy in enemy_collide:
            # Remove the coin
            self.player_sprite.remove_from_sprite_lists()

        # Changing x coordinate of player
        self.player_sprite.center_x += self.vel_x * delta_time

        # Updating the physics engine to move the player
        self.physics_engine.update()

        # Calling the camera_move function
        self.camera_move()

    # Creating function to change the velocity
    # when button is pressed
    def on_key_press(self, symbol, modifier):

        # Checking the button pressed
        # and changing the value of velocity
        if symbol == arcade.key.LEFT:
            self.vel_x = -300
        elif symbol == arcade.key.RIGHT:
            self.vel_x = 300
        elif symbol == arcade.key.UP:
            if self.physics_engine.can_jump():
                self.player_sprite.change_y = 15

    # Creating function to change the velocity
    # when button is released
    def on_key_release(self, symbol, modifier):

        # Checking the button released
        # and changing the value of velocity
        if symbol == arcade.key.LEFT:
            self.vel_x = 0
        elif symbol == arcade.key.RIGHT:
            self.vel_x = 0

    def camera_move(self):

        # Getting the x coordinate for the center of camera
        screen_x = self.player_sprite.center_x - \
            (self.camera.viewport_width / 2)

        # Getting the y coordinate for the center of camera
        screen_y = self.player_sprite.center_y - \
            (self.camera.viewport_height / 2)

        # Moving the camera
        self.camera.move_to([screen_x, screen_y])


# Calling MainGame class
game = MainGame()
game.setup()
arcade.run()

Output:

Killing the Enemy

Now we want to kill the enemy when the player jumps on top of it. For this, we will check if the bottom other player is equal to the top of the enemy or not. If it is equal then we will remove the layer sprite.

• For this first, we will store the coordinate of the bottom of the player in a variable.

Syntax:

x = int(self.player_sprite.center_y – 14)

• Similarly the coordinate of the top of the enemy in a different variable.

Syntax:

y = int(self.enemy.center_y + 25)

• Then, if x and y are equal and the enemy and player are colliding then we will remove our enemy sprite.

Syntax:

if x == y:

  self.enemy.remove_from_sprite_lists()

Example: Killing an enemy using Arcade

Python3

# Importing arcade module
import arcade

# Creating MainGame class
class MainGame(arcade.Window):
    def __init__(self):
        super().__init__(600, 600,
                         title="Player Movement")

        # Initializing a variable to store
        # the velocity of the player
        self.vel_x = 0

        # Creating variable for Camera
        self.camera = None

        # Creating variable to store current score
        self.score = 0

        # Creating variable to move the enemy
        self.enemy_move = 2

        # Creating variable for enemy sprite
        self.enemy = None

        # Creating scene object
        self.scene = None

        # Creating variable to store player sprite
        self.player = None

        # Creating variable for our game engine
        self.physics_engine = None

    # Creating on_draw() function to draw on the screen
    def on_draw(self):
        arcade.start_render()

        # Drawing the text
        arcade.draw_text('Score :- '+str(self.score),
                         self.player_sprite.center_x - 500 / 2,
                         self.player_sprite.center_y + 200,
                         arcade.color.WHITE, 30, 5000, 'left')

        # Using the camera
        self.camera.use()

        # Drawing our scene
        self.scene.draw()

    def setup(self):

         # Initialize Scene object
        self.scene = arcade.Scene()

        # Using Camera() function
        self.camera = arcade.Camera(600, 600)

        # Loading enemy sprite
        self.enemy = arcade.Sprite("Enemy.png", 1)

        # Initializing the starting coordinates
        self.enemy.center_x = 500
        self.enemy.center_y = 110

        # Adding the enemy sprite in the scene
        self.scene.add_sprite("Enemy", self.enemy)

        # Creating different sprite lists
        self.scene.add_sprite_list("Player")
        self.scene.add_sprite_list("Platforms",
                                   use_spatial_hash=True)

        # Adding player sprite
        self.player_sprite = arcade.Sprite("Player.png", 1)

        # Adding coordinates for the center of the sprite
        self.player_sprite.center_x = 64
        self.player_sprite.center_y = 90

        # Adding Sprite in our scene
        self.scene.add_sprite("Player", self.player_sprite)

        # Adding platform sprite according to level
        platform = arcade.Sprite(f"Platform.png", 1)

        # Adding coordinates for the center of the platform
        platform.center_x = 300
        platform.center_y = 32
        self.scene.add_sprite("Platforms", platform)

        # Creating Physics engine
        self.physics_engine = arcade.PhysicsEnginePlatformer(
            self.player_sprite, self.scene.get_sprite_list("Platforms"), 0.5
        )

    # Creating on_update function to
    # update the x coordinate

    def on_update(self, delta_time):

        # Moving the position of enemy
        self.enemy.center_x += self.enemy_move

        # Changing the direction of enemy movement
        if self.enemy.center_x > 500 or self.enemy.center_x < 160:
            self.enemy_move *= -1

        # Checking if the enemy is colliding with player or not
        enemy_collide = arcade.check_for_collision_with_list(
            self.player_sprite, self.scene.get_sprite_list("Enemy")
        )

        # Looping through each enemy and removing the player if colliding
        for enemy in enemy_collide:

            # Checking the top of enemy and bottom of player
            x = int(self.player_sprite.center_y - 14)
            y = int(self.enemy.center_y + 25)
            if x == y:
                self.enemy.remove_from_sprite_lists()
            else:
                # Remove the coin
                self.player_sprite.remove_from_sprite_lists()

        # Changing x coordinate of player
        self.player_sprite.center_x += self.vel_x * delta_time

        # Updating the physics engine to move the player
        self.physics_engine.update()

        # Calling the camera_move function
        self.camera_move()

    # Creating function to change the velocity
    # when button is pressed
    def on_key_press(self, symbol, modifier):

        # Checking the button pressed
        # and changing the value of velocity
        if symbol == arcade.key.LEFT:
            self.vel_x = -300
        elif symbol == arcade.key.RIGHT:
            self.vel_x = 300
        elif symbol == arcade.key.UP:
            if self.physics_engine.can_jump():
                self.player_sprite.change_y = 15

    # Creating function to change the velocity
    # when button is released
    def on_key_release(self, symbol, modifier):

        # Checking the button released
        # and changing the value of velocity
        if symbol == arcade.key.LEFT:
            self.vel_x = 0
        elif symbol == arcade.key.RIGHT:
            self.vel_x = 0

    def camera_move(self):

        # Getting the x coordinate for the center of camera
        screen_x = self.player_sprite.center_x - \
            (self.camera.viewport_width / 2)

        # Getting the y coordinate for the center of camera
        screen_y = self.player_sprite.center_y - \
            (self.camera.viewport_height / 2)

        # Moving the camera
        self.camera.move_to([screen_x, screen_y])


# Calling MainGame class
game = MainGame()
game.setup()
arcade.run()

Output: