21. Platformers

Ever wanted to create your own platformer? It isn’t too hard! Here’s an example to get started.

21.1. Map File

First, we need a map. This is a “map” file created with the Tiled program. The program is free. You can download it and use it to create your map file.

In this map file the numbers represent:

Number Item
-1 Empty square
0 Crate
1 Left grass corner
2 Middle grass corner
3 Right grass corner

You can download these tiles (originally from kenney.nl) here:

../../_images/boxCrate_double1.png ../../_images/grassLeft.png ../../_images/grassMid.png ../../_images/grassRight.png

Of course, you’ll need a character to jump around the map:

../../_images/character2.png

Here is the map file:

map.csv
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-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1
-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,0,-1,-1
-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,0,0,-1,-1,-1,-1,-1,0,-1,-1
0,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,1,2,3,-1,0,-1,-1,-1,1,2,3,-1,-1,-1,-1,-1,0,0,-1,-1,-1,1,2,3,-1,-1,-1,0,0,-1,-1,-1,-1,-1,0,-1,-1
0,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,0,-1,-1,-1,-1,0,0,0,-1,-1,-1,0,-1,-1,-1,-1,-1,-1,0,0,0,-1,-1,-1,-1,-1,-1,-1,-1,0,0,0,-1,-1,1,2,3,-1,-1
0,-1,-1,0,-1,0,-1,0,-1,-1,0,0,0,-1,-1,0,0,0,0,0,-1,-1,0,-1,-1,-1,0,-1,-1,0,0,0,-1,-1,0,-1,-1,-1,-1,-1,0,0,0,0,-1,-1,-1,-1,-1,-1
1,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,3

The Tiled program takes some getting used to. You start off with a screen like this:

../../_images/tiled_new_file.png

Most of the tiles from kenney.nl are 128x128 pixels. In the image above I’ve got a 7 tile high, by 50 pixel wide side-scroll map.

After this, you have to create a new “tile set.” These will be all the images for your map, and the numbers they associate with:

../../_images/tiled_new_tileset.png

The numbers of the tiles correspond to the order you added the tiles. I don’t think you can change the mapping after you create the tileset.

Next, you “paint” your map:

../../_images/tiled_make_map.png

When you are done, you can “Export as” a CSV file.

21.2. Python Program

Platformer example, simple
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"""
Load a map stored in csv format, as exported by the program 'Tiled.'

Artwork from: http://kenney.nl
Tiled available from: http://www.mapeditor.org/
"""
import arcade

SPRITE_SCALING = 0.5

SCREEN_WIDTH = 800
SCREEN_HEIGHT = 600

# How many pixels to keep as a minimum margin between the character
# and the edge of the screen.
VIEWPORT_MARGIN = 40
RIGHT_MARGIN = 150

# Physics
MOVEMENT_SPEED = 5
JUMP_SPEED = 14
GRAVITY = 0.5


def get_map(filename):
    """
    This function loads an array based on a map stored as a list of
    numbers separated by commas.
    """

    # Open the file
    map_file = open(filename)

    # Create an empty list of rows that will hold our map
    map_array = []

    # Read in a line from the file
    for line in map_file:

        # Strip the whitespace, and \n at the end
        line = line.strip()

        # This creates a list by splitting line everywhere there is a comma.
        map_row = line.split(",")

        # The list currently has all the numbers stored as text, and we want it
        # as a number. (e.g. We want 1 not "1"). So loop through and convert
        # to an integer.
        for index, item in enumerate(map_row):
            map_row[index] = int(item)

        # Now that we've completed processing the row, add it to our map array.
        map_array.append(map_row)

    # Done, return the map.
    return map_array


class MyWindow(arcade.Window):
    """ Main application class. """

    def __init__(self):
        """
        Initializer
        """
        # Call the parent class
        super().__init__(SCREEN_WIDTH, SCREEN_HEIGHT)

        # Sprite lists
        self.all_sprites_list = None
        self.coin_list = None
        self.wall_list = None

        # Set up the player
        self.player_sprite = None

        # Physics engine
        self.physics_engine = None

        # Used for scrolling map
        self.view_left = 0
        self.view_bottom = 0

    def setup(self):
        """ Set up the game and initialize the variables. """

        # Sprite lists
        self.all_sprites_list = arcade.SpriteList()
        self.wall_list = arcade.SpriteList()

        # Set up the player
        self.player_sprite = arcade.Sprite("character.png", SPRITE_SCALING)

        # Starting position of the player
        self.player_sprite.center_x = 90
        self.player_sprite.center_y = 270
        self.all_sprites_list.append(self.player_sprite)

        # Get a 2D array made of numbers based on the map
        map_array = get_map("map.csv")

        # Now that we've got the map, loop through and create the sprites
        for row_index in range(len(map_array)):
            for column_index in range(len(map_array[row_index])):

                item = map_array[row_index][column_index]

                # For this map, the numbers represent:
                # -1 = empty
                # 0  = box
                # 1  = grass left edge
                # 2  = grass middle
                # 3  = grass right edge
                if item == 0:
                    wall = arcade.Sprite("boxCrate_double.png", SPRITE_SCALING)
                elif item == 1:
                    wall = arcade.Sprite("grassLeft.png", SPRITE_SCALING)
                elif item == 2:
                    wall = arcade.Sprite("grassMid.png", SPRITE_SCALING)
                elif item == 3:
                    wall = arcade.Sprite("grassRight.png", SPRITE_SCALING)

                if item >= 0:
                    # Calculate where the sprite goes
                    wall.left = column_index * 64
                    wall.top = (7 - row_index) * 64

                    # Add the sprite
                    self.all_sprites_list.append(wall)
                    self.wall_list.append(wall)

        self.physics_engine = arcade.PhysicsEnginePlatformer(self.player_sprite,
                                                             self.wall_list,
                                                             gravity_constant=GRAVITY)

        # Set the background color
        arcade.set_background_color(arcade.color.AMAZON)

        # Set the view port boundaries
        # These numbers set where we have 'scrolled' to.
        self.view_left = 0
        self.view_bottom = 0

    def on_draw(self):
        """
        Render the screen.
        """

        # This command has to happen before we start drawing
        arcade.start_render()

        # Draw all the sprites.
        self.all_sprites_list.draw()

    def on_key_press(self, key, modifiers):
        """
        Called whenever the mouse moves.
        """
        if key == arcade.key.UP:
            # This line below is new. It checks to make sure there is a platform underneath
            # the player. Because you can't jump if there isn't ground beneath your feet.
            if self.physics_engine.can_jump():
                self.player_sprite.change_y = JUMP_SPEED
        elif key == arcade.key.LEFT:
            self.player_sprite.change_x = -MOVEMENT_SPEED
        elif key == arcade.key.RIGHT:
            self.player_sprite.change_x = MOVEMENT_SPEED

    def on_key_release(self, key, modifiers):
        """
        Called when the user presses a mouse button.
        """
        if key == arcade.key.LEFT or key == arcade.key.RIGHT:
            self.player_sprite.change_x = 0

    def update(self, delta_time):
        """ Movement and game logic """

        self.physics_engine.update()

        # --- Manage Scrolling ---

        # Track if we need to change the view port

        changed = False

        # Scroll left
        left_bndry = self.view_left + VIEWPORT_MARGIN
        if self.player_sprite.left < left_bndry:
            self.view_left -= left_bndry - self.player_sprite.left
            changed = True

        # Scroll right
        right_bndry = self.view_left + SCREEN_WIDTH - RIGHT_MARGIN
        if self.player_sprite.right > right_bndry:
            self.view_left += self.player_sprite.right - right_bndry
            changed = True

        # Scroll up
        top_bndry = self.view_bottom + SCREEN_HEIGHT - VIEWPORT_MARGIN
        if self.player_sprite.top > top_bndry:
            self.view_bottom += self.player_sprite.top - top_bndry
            changed = True

        # Scroll down
        bottom_bndry = self.view_bottom + VIEWPORT_MARGIN
        if self.player_sprite.bottom < bottom_bndry:
            self.view_bottom -= bottom_bndry - self.player_sprite.bottom
            changed = True

        # If we need to scroll, go ahead and do it.
        if changed:
            arcade.set_viewport(self.view_left,
                                SCREEN_WIDTH + self.view_left,
                                self.view_bottom,
                                SCREEN_HEIGHT + self.view_bottom)


def main():
    window = MyWindow()
    window.setup()

    arcade.run()


main()
Platformer example, slightly more complex and “Pythonic”
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"""
Load a map stored in csv format, as exported by the program 'Tiled.'

Artwork from: http://kenney.nl
Tiled available from: http://www.mapeditor.org/
"""
import arcade

SPRITE_SCALING = 0.5

SCREEN_WIDTH = 800
SCREEN_HEIGHT = 600

# How many pixels to keep as a minimum margin between the character
# and the edge of the screen.
VIEWPORT_MARGIN = 40
RIGHT_MARGIN = 150

# Physics
MOVEMENT_SPEED = 5
JUMP_SPEED = 14
GRAVITY = 0.5


def get_map(filename):
    """
    This function loads an array based on a map stored as a list of
    numbers separated by commas.
    """

    # Open the file
    map_file = open(filename)

    # Create an empty list of rows that will hold our map
    map_array = []

    # Read in a line from the file
    for line in map_file:

        # Strip the whitespace, and \n at the end
        line = line.strip()

        # This creates a list by splitting line everywhere there is a comma.
        map_row = line.split(",")

        # The list currently has all the numbers stored as text, and we want it
        # as a number. (e.g. We want 1 not "1"). So loop through and convert
        # to an integer.
        for index, item in enumerate(map_row):
            map_row[index] = int(item)

        # Now that we've completed processing the row, add it to our map array.
        map_array.append(map_row)

    # Done, return the map.
    return map_array


class MyWindow(arcade.Window):
    """ Main application class. """

    def __init__(self, width, height):
        """
        Initializer
        """
        # Call the parent class
        super().__init__(width, height)

        # Sprite lists
        self.all_sprites_list = None
        self.coin_list = None
        self.wall_list = None

        # Set up the player
        self.score = 0
        self.player_sprite = None

        # Physics engine
        self.physics_engine = None

        # Used for scrolling map
        self.view_left = 0
        self.view_bottom = 0

        # When the user gets far enough, we'll print "Game Over"
        self.game_over = False

    def setup(self):
        """ Set up the game and initialize the variables. """

        # Sprite lists
        self.all_sprites_list = arcade.SpriteList()
        self.wall_list = arcade.SpriteList()

        # Set up the player
        self.score = 0
        self.player_sprite = arcade.Sprite("character.png", SPRITE_SCALING)

        # Starting position of the player
        self.player_sprite.center_x = 64
        self.player_sprite.center_y = 270
        self.all_sprites_list.append(self.player_sprite)

        # Get a 2D array made of numbers based on the map
        map_array = get_map("map.csv")

        # Now that we've got the map, loop through and create the sprites
        for row_index, row in enumerate(map_array):
            for column_index, item in enumerate(row):

                # For this map, the numbers represent:
                # -1 = empty
                # 0  = box
                # 1  = grass left edge
                # 2  = grass middle
                # 3  = grass right edge
                if item == -1:
                    continue
                elif item == 0:
                    wall = arcade.Sprite("boxCrate_double.png", SPRITE_SCALING)
                elif item == 1:
                    wall = arcade.Sprite("grassLeft.png", SPRITE_SCALING)
                elif item == 2:
                    wall = arcade.Sprite("grassMid.png", SPRITE_SCALING)
                elif item == 3:
                    wall = arcade.Sprite("grassRight.png", SPRITE_SCALING)

                # Calculate where the sprite goes
                wall.right = column_index * 64
                wall.top = (7 - row_index) * 64

                # Add the sprite
                self.all_sprites_list.append(wall)
                self.wall_list.append(wall)

        self.physics_engine = arcade.PhysicsEnginePlatformer(self.player_sprite,
                                                             self.wall_list,
                                                             gravity_constant=GRAVITY)

        # Set the background color
        arcade.set_background_color(arcade.color.AMAZON)

        # Set the view port boundaries
        # These numbers set where we have 'scrolled' to.
        self.view_left = 0
        self.view_bottom = 0

        self.game_over = False

    def on_draw(self):
        """
        Render the screen.
        """

        # This command has to happen before we start drawing
        arcade.start_render()

        # Draw all the sprites.
        self.all_sprites_list.draw()

        # Put the text on the screen.
        # Adjust the text position based on the view port so that we don't
        # scroll the text too.
        distance = self.view_left + self.player_sprite.right
        output = f"Distance: {distance}"
        arcade.draw_text(output, self.view_left + 10, self.view_bottom + 20, arcade.color.WHITE, 14)

        if self.game_over:
            output = "Game Over"
            arcade.draw_text(output, self.view_left + 200,
                             self.view_bottom + 200,
                             arcade.color.WHITE, 30)

    def on_key_press(self, key, modifiers):
        """
        Called whenever the mouse moves.
        """
        if key == arcade.key.UP:
            # This line below is new. It checks to make sure there is a platform underneath
            # the player. Because you can't jump if there isn't ground beneath your feet.
            if self.physics_engine.can_jump():
                self.player_sprite.change_y = JUMP_SPEED
        elif key == arcade.key.LEFT:
            self.player_sprite.change_x = -MOVEMENT_SPEED
        elif key == arcade.key.RIGHT:
            self.player_sprite.change_x = MOVEMENT_SPEED

    def on_key_release(self, key, modifiers):
        """
        Called when the user presses a mouse button.
        """
        if key == arcade.key.LEFT or key == arcade.key.RIGHT:
            self.player_sprite.change_x = 0

    def update(self, delta_time):
        """ Movement and game logic """

        if self.view_left + self.player_sprite.right >= 5630:
            self.game_over = True

        # Call update on all sprites (The sprites don't do much in this
        # example though.)
        if not self.game_over:
            self.physics_engine.update()

        # --- Manage Scrolling ---

        # Track if we need to change the view port

        changed = False

        # Scroll left
        left_bndry = self.view_left + VIEWPORT_MARGIN
        if self.player_sprite.left < left_bndry:
            self.view_left -= left_bndry - self.player_sprite.left
            changed = True

        # Scroll right
        right_bndry = self.view_left + SCREEN_WIDTH - RIGHT_MARGIN
        if self.player_sprite.right > right_bndry:
            self.view_left += self.player_sprite.right - right_bndry
            changed = True

        # Scroll up
        top_bndry = self.view_bottom + SCREEN_HEIGHT - VIEWPORT_MARGIN
        if self.player_sprite.top > top_bndry:
            self.view_bottom += self.player_sprite.top - top_bndry
            changed = True

        # Scroll down
        bottom_bndry = self.view_bottom + VIEWPORT_MARGIN
        if self.player_sprite.bottom < bottom_bndry:
            self.view_bottom -= bottom_bndry - self.player_sprite.bottom
            changed = True

        # If we need to scroll, go ahead and do it.
        if changed:
            arcade.set_viewport(self.view_left,
                                SCREEN_WIDTH + self.view_left,
                                self.view_bottom,
                                SCREEN_HEIGHT + self.view_bottom)


def main():
    window = MyWindow(SCREEN_WIDTH, SCREEN_HEIGHT)
    window.setup()

    arcade.run()


main()

21.3. Other Examples

If you are looking for platforms that move, see Sprite Moving Platforms.

If you are looking to be able to create ramps you can run up and down, see Sprite Ramps.