Python Arcade - Adding Ladders

Last Updated : 17 Oct, 2021

In this article, we will learn how to add ladders in Arcade using Python.

Adding Ladder

In this example, we are going to add one ladder on the screen which our player can climb. For this, we will use some functions:

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

PhysicsEnginePlatformer(): Simplistic physics engine for use in a platformer.

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():

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, scene, ladder sprite, and player's sprite then we will create 4 functions inside this class.

on_draw(): Inside this function, we will use our scene on the screen.
setup(): In this function, we will initialize our scene object then we will load our player and platform's sprites then we will load our ladder sprite and initialize the starting x and y coordinate. After that, we will call the PhysicsEnginePlatformer() function. We will pass our ladder as a parameter in our PhysicsEnginePlatformer() function.
on_update(): In this function, we will update the physics engine and the x coordinates of the player's 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.

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 ladder sprite
        self.ladder = 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 our scene
        self.scene.draw()

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

        # Loading ladder sprite
        self.ladder = arcade.Sprite("Ladder.png", 1)

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

        # Adding the ladder sprite in the scene
        self.scene.add_sprite("Ladder", self.ladder)

        # 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, self.scene.get_sprite_list("Ladder")
        )

    # 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()

    # 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.is_on_ladder():
                self.player_sprite.change_y = 2
            elif self.physics_engine.can_jump():
                self.player_sprite.change_y = 15
        elif symbol == arcade.key.DOWN:
            if self.physics_engine.is_on_ladder():
                self.player_sprite.change_y = -2

    # 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
        elif symbol == arcade.key.UP or symbol == arcade.key.DOWN:
            if self.physics_engine.is_on_ladder():
                self.player_sprite.change_y = 0


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