Python Arcade – Adding Moving Platforms

In this article, we will discuss how to add moving platforms to our arcade games in Python.

Adding Moving Platform

We can easily add moving platforms in our arcade game by following the below steps:

• Create 2 new variables for sprite and velocity of moving platform.

self.moving_vel = 3
self.moving_platform = None

• Load the sprite and add the initial coordinates.

self.moving_platform = arcade.Sprite("Moving.png",1)
self.moving_platform.center_x = 500
self.moving_platform.center_y = 500

• Update the y-coordinate of the platform.

self.moving_platform.center_y -= self.moving_vel

• Change the direction of the platform if the platform crosses the boundary.

if self.moving_platform.center_y < 100 or self.moving_platform.center_y>600:
   self.moving_vel *= -1

Sprites Used:

For this, we are going to create a MainGame() class. Inside this class first, we are going to initialize some variables for player’s velocity, platform velocity, camera, player sprite, physics engine, and our scene. After that, we will create 6 functions inside this class.

• on_draw(): Inside this function, we will use our camera, and then we will draw our scene.
• setup(): In this function, we will initialize our camera and scene object then we will load our player and platform’s sprites. After that, we will call the  PhysicsEnginePlatformer() function.
• on_update(): In this function, we will update the x coordinate of the player’s sprite by adding the value of the velocity variable and we also update the y coordinate of our moving platform. After that, we will call our camera_move() function.
• on_key_press(): In this function, we will change the value of the vel_x  variable according to the keyboard key that is pressed.
• on_key_release(): In this function, we will change the value of the vel_x variable according to the keyboard key that is released.
• camera_move(): In this function, we will change the position of the camera according to the current position of the player.

Below is the implementation:

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 for moving velocity
        self.moving_vel = 3

        # Creating variable for Platform
        self.moving_platform = 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()

        # 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)

        # 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 = 600

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

        #Adding moving Platform sprite
        self.moving_platform = arcade.Sprite("Moving.png",1)

        # Adding starting coordinates
        self.moving_platform.center_x = 500
        self.moving_platform.center_y = 500

        # Adding to Platforms sprite group
        self.scene.add_sprite("Platforms",  self.moving_platform)

        # 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):

        # 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()

        # Adding moving velocity in moving platform
        self.moving_platform.center_y -= self.moving_vel

        # Changing the direction
        if self.moving_platform.center_y < 100 or
        self.moving_platform.center_y>600:
            self.moving_vel *= -1

        # 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: