Creating a Recursive Maze

Screen shot of a maze created by recursion
maze_recursive.py
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"""
Create a maze using a recursive division method.

For more information on the algorithm, see "Recursive Division Method"
at https://en.wikipedia.org/wiki/Maze_generation_algorithm

Artwork from http://kenney.nl

If Python and Arcade are installed, this example can be run from the command line with:
python -m arcade.examples.maze_depth_first
"""
import random
import arcade
import timeit
import os

NATIVE_SPRITE_SIZE = 128
SPRITE_SCALING = 0.25
SPRITE_SIZE = NATIVE_SPRITE_SIZE * SPRITE_SCALING

SCREEN_WIDTH = 1000
SCREEN_HEIGHT = 700

MOVEMENT_SPEED = 8

TILE_EMPTY = 0
TILE_CRATE = 1

# Maze must have an ODD number of rows and columns.
# Walls go on EVEN rows/columns.
# Openings go on ODD rows/columns
MAZE_HEIGHT = 51
MAZE_WIDTH = 51


# How many pixels to keep as a minimum margin between the character
# and the edge of the screen.
VIEWPORT_MARGIN = 200

MERGE_SPRITES = True

def create_empty_grid(width, height, default_value=TILE_EMPTY):
    """ Create an empty grid. """
    grid = []
    for row in range(height):
        grid.append([])
        for column in range(width):
            grid[row].append(default_value)
    return grid


def create_outside_walls(maze):
    """ Create outside border walls."""

    # Create left and right walls
    for row in range(len(maze)):
        maze[row][0] = TILE_CRATE
        maze[row][len(maze[row])-1] = TILE_CRATE

    # Create top and bottom walls
    for column in range(1, len(maze[0]) - 1):
        maze[0][column] = TILE_CRATE
        maze[len(maze) - 1][column] = TILE_CRATE


def make_maze_recursive_call(maze, top, bottom, left, right):
    """
    Recursive function to divide up the maze in four sections
    and create three gaps.
    Walls can only go on even numbered rows/columns.
    Gaps can only go on odd numbered rows/columns.
    Maze must have an ODD number of rows and columns.
    """

    # Figure out where to divide horizontally
    start_range = bottom + 2
    end_range = top - 1
    y = random.randrange(start_range, end_range, 2)

    # Do the division
    for column in range(left + 1, right):
        maze[y][column] = TILE_CRATE

    # Figure out where to divide vertically
    start_range = left + 2
    end_range = right - 1
    x = random.randrange(start_range, end_range, 2)

    # Do the division
    for row in range(bottom + 1, top):
        maze[row][x] = TILE_CRATE

    # Now we'll make a gap on 3 of the 4 walls.
    # Figure out which wall does NOT get a gap.
    wall = random.randrange(4)
    if wall != 0:
        gap = random.randrange(left + 1, x, 2)
        maze[y][gap] = TILE_EMPTY

    if wall != 1:
        gap = random.randrange(x + 1, right, 2)
        maze[y][gap] = TILE_EMPTY

    if wall != 2:
        gap = random.randrange(bottom + 1, y, 2)
        maze[gap][x] = TILE_EMPTY

    if wall != 3:
        gap = random.randrange(y + 1, top, 2)
        maze[gap][x] = TILE_EMPTY

    # If there's enough space, to a recursive call.
    if top > y + 3 and x > left + 3:
        make_maze_recursive_call(maze, top, y, left, x)

    if top > y + 3 and x + 3 < right:
        make_maze_recursive_call(maze, top, y, x, right)

    if bottom + 3 < y and x + 3 < right:
        make_maze_recursive_call(maze, y, bottom, x, right)

    if bottom + 3 < y and x > left + 3:
        make_maze_recursive_call(maze, y, bottom, left, x)


def make_maze_recursion(maze_width, maze_height):
    """ Make the maze by recursively splitting it into four rooms. """
    maze = create_empty_grid(maze_width, maze_height)
    # Fill in the outside walls
    create_outside_walls(maze)

    # Start the recursive process
    make_maze_recursive_call(maze, maze_height - 1, 0, 0, maze_width - 1)
    return maze


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

    def __init__(self, width, height):
        """
        Initializer
        """
        super().__init__(width, height)

        # Set the working directory (where we expect to find files) to the same
        # directory this .py file is in. You can leave this out of your own
        # code, but it is needed to easily run the examples using "python -m"
        # as mentioned at the top of this program.
        file_path = os.path.dirname(os.path.abspath(__file__))
        os.chdir(file_path)

        # Sprite lists
        self.player_list = None
        self.wall_list = None

        # Player info
        self.score = 0
        self.player_sprite = None

        # Physics engine
        self.physics_engine = None

        # Used to scroll
        self.view_bottom = 0
        self.view_left = 0

        # Time to process
        self.processing_time = 0
        self.draw_time = 0

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

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

        # Set up the player
        self.score = 0

        maze = make_maze_recursion(MAZE_WIDTH, MAZE_HEIGHT)

        # Create sprites based on 2D grid
        if not MERGE_SPRITES:
            # This is the simple-to-understand method. Each grid location
            # is a sprite.
            for row in range(MAZE_HEIGHT):
                for column in range(MAZE_WIDTH):
                    if maze[row][column] == 1:
                        wall = arcade.Sprite("images/grassCenter.png", SPRITE_SCALING)
                        wall.center_x = column * SPRITE_SIZE + SPRITE_SIZE / 2
                        wall.center_y = row * SPRITE_SIZE + SPRITE_SIZE / 2
                        self.wall_list.append(wall)
        else:
            # This uses new Arcade 1.3.1 features, that allow me to create a
            # larger sprite with a repeating texture. So if there are multiple
            # cells in a row with a wall, we merge them into one sprite, with a
            # repeating texture for each cell. This reduces our sprite count.
            for row in range(MAZE_HEIGHT):
                column = 0
                while column < len(maze):
                    while column < len(maze) and maze[row][column] == 0:
                        column += 1
                    start_column = column
                    while column < len(maze) and maze[row][column] == 1:
                        column += 1
                    end_column = column - 1

                    column_count = end_column - start_column + 1
                    column_mid = (start_column + end_column) / 2

                    wall = arcade.Sprite("images/grassCenter.png", SPRITE_SCALING,
                                         repeat_count_x=column_count)
                    wall.center_x = column_mid * SPRITE_SIZE + SPRITE_SIZE / 2
                    wall.center_y = row * SPRITE_SIZE + SPRITE_SIZE / 2
                    wall.width = SPRITE_SIZE * column_count
                    self.wall_list.append(wall)

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

        # Randomly place the player. If we are in a wall, repeat until we aren't.
        placed = False
        while not placed:

            # Randomly position
            self.player_sprite.center_x = random.randrange(MAZE_WIDTH * SPRITE_SIZE)
            self.player_sprite.center_y = random.randrange(MAZE_HEIGHT * SPRITE_SIZE)

            # Are we in a wall?
            walls_hit = arcade.check_for_collision_with_list(self.player_sprite, self.wall_list)
            if len(walls_hit) == 0:
                # Not in a wall! Success!
                placed = True

        self.physics_engine = arcade.PhysicsEngineSimple(self.player_sprite, self.wall_list)

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

        # Set the viewport boundaries
        # These numbers set where we have 'scrolled' to.
        self.view_left = 0
        self.view_bottom = 0
        print(f"Total wall blocks: {len(self.wall_list)}")

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

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

        # Start timing how long this takes
        draw_start_time = timeit.default_timer()

        # Draw all the sprites.
        self.wall_list.draw()
        self.player_list.draw()

        # Draw info on the screen
        sprite_count = len(self.wall_list)

        output = f"Sprite Count: {sprite_count}"
        arcade.draw_text(output,
                         self.view_left + 20,
                         SCREEN_HEIGHT - 20 + self.view_bottom,
                         arcade.color.WHITE, 16)

        output = f"Drawing time: {self.draw_time:.3f}"
        arcade.draw_text(output,
                         self.view_left + 20,
                         SCREEN_HEIGHT - 40 + self.view_bottom,
                         arcade.color.WHITE, 16)

        output = f"Processing time: {self.processing_time:.3f}"
        arcade.draw_text(output,
                         self.view_left + 20,
                         SCREEN_HEIGHT - 60 + self.view_bottom,
                         arcade.color.WHITE, 16)

        self.draw_time = timeit.default_timer() - draw_start_time

    def on_key_press(self, key, modifiers):
        """Called whenever a key is pressed. """

        if key == arcade.key.UP:
            self.player_sprite.change_y = MOVEMENT_SPEED
        elif key == arcade.key.DOWN:
            self.player_sprite.change_y = -MOVEMENT_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 releases a key. """

        if key == arcade.key.UP or key == arcade.key.DOWN:
            self.player_sprite.change_y = 0
        elif key == arcade.key.LEFT or key == arcade.key.RIGHT:
            self.player_sprite.change_x = 0

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

        start_time = timeit.default_timer()

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

        # --- Manage Scrolling ---

        # Track if we need to change the viewport

        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 - VIEWPORT_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 changed:
            arcade.set_viewport(self.view_left,
                                SCREEN_WIDTH + self.view_left,
                                self.view_bottom,
                                SCREEN_HEIGHT + self.view_bottom)

        # Save the time it took to do this.
        self.processing_time = timeit.default_timer() - start_time


def main():
    """ Main method """
    window = MyGame(SCREEN_WIDTH, SCREEN_HEIGHT)
    window.setup()
    arcade.run()


if __name__ == "__main__":
    main()