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10.2: Source Code to Star Pusher

  • Page ID
    13619

    \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

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    \(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)

    This source code can be downloaded from http://invpy.com/starpusher.py. If you get any error messages, look at the line number that is mentioned in the error message and check your code for any typos. You can also copy and paste your code into the web form at http://invpy.com/diff/starpusher to see if the differences between your code and the code in the book.

    The level file can be downloaded from http://invpy.com/starPusherLevels.txt. The tiles can be downloaded from http://invpy.com/starPusherImages.zip.

    Also, just like the squirrel, grass, and enemy "objects" in the Squirrel Eat Squirrel game, when I say "map objects", "game state objects", or "level objects" in this chapter, I do not mean objects in the Object-Oriented Programming sense. These "objects" are really just dictionary values, but it is easier to refer to them as objects since they represent things in the game world.

    # Star Pusher (a Sokoban clone)
    # By Al Sweigart al@inventwithpython.com
    # http://inventwithpython.com/pygame
    # Released under a "Simplified BSD" license
    
    import random, sys, copy, os, pygame
    from pygame.locals import *
    
    FPS = 30 # frames per second to update the screen
    WINWIDTH = 800 # width of the program's window, in pixels
    WINHEIGHT = 600 # height in pixels
    HALF_WINWIDTH = int(WINWIDTH / 2)
    HALF_WINHEIGHT = int(WINHEIGHT / 2)
    
    # The total width and height of each tile in pixels.
    TILEWIDTH = 50
    TILEHEIGHT = 85
    TILEFLOORHEIGHT = 40
    
    CAM_MOVE_SPEED = 5 # how many pixels per frame the camera moves
    
    # The percentage of outdoor tiles that have additional
    # decoration on them, such as a tree or rock.
    OUTSIDE_DECORATION_PCT = 20
    
    BRIGHTBLUE = (  0, 170, 255)
    WHITE      = (255, 255, 255)
    BGCOLOR = BRIGHTBLUE
    TEXTCOLOR = WHITE
    
    UP = 'up'
    DOWN = 'down'
    LEFT = 'left'
    RIGHT = 'right'
    
    
    def main():
        global FPSCLOCK, DISPLAYSURF, IMAGESDICT, TILEMAPPING, OUTSIDEDECOMAPPING, BASICFONT, PLAYERIMAGES, currentImage
    
        # Pygame initialization and basic set up of the global variables.
        pygame.init()
        FPSCLOCK = pygame.time.Clock()
    
        # Because the Surface object stored in DISPLAYSURF was returned
        # from the pygame.display.set_mode() function, this is the
        # Surface object that is drawn to the actual computer screen
        # when pygame.display.update() is called.
        DISPLAYSURF = pygame.display.set_mode((WINWIDTH, WINHEIGHT))
    
        pygame.display.set_caption('Star Pusher')
        BASICFONT = pygame.font.Font('freesansbold.ttf', 18)
    
        # A global dict value that will contain all the Pygame
        # Surface objects returned by pygame.image.load().
        IMAGESDICT = {'uncovered goal': pygame.image.load('RedSelector.png'),
                      'covered goal': pygame.image.load('Selector.png'),
                      'star': pygame.image.load('Star.png'),
                      'corner': pygame.image.load('Wall_Block_Tall.png'),
                      'wall': pygame.image.load('Wood_Block_Tall.png'),
                      'inside floor': pygame.image.load('Plain_Block.png'),
                      'outside floor': pygame.image.load('Grass_Block.png'),
                      'title': pygame.image.load('star_title.png'),
                      'solved': pygame.image.load('star_solved.png'),
                      'princess': pygame.image.load('princess.png'),
                      'boy': pygame.image.load('boy.png'),
                      'catgirl': pygame.image.load('catgirl.png'),
                      'horngirl': pygame.image.load('horngirl.png'),
                      'pinkgirl': pygame.image.load('pinkgirl.png'),
                      'rock': pygame.image.load('Rock.png'),
                      'short tree': pygame.image.load('Tree_Short.png'),
                      'tall tree': pygame.image.load('Tree_Tall.png'),
                      'ugly tree': pygame.image.load('Tree_Ugly.png')}
    
        # These dict values are global, and map the character that appears
        # in the level file to the Surface object it represents.
        TILEMAPPING = {'x': IMAGESDICT['corner'],
                       '#': IMAGESDICT['wall'],
                       'o': IMAGESDICT['inside floor'],
                       ' ': IMAGESDICT['outside floor']}
        OUTSIDEDECOMAPPING = {'1': IMAGESDICT['rock'],
                              '2': IMAGESDICT['short tree'],
                              '3': IMAGESDICT['tall tree'],
                              '4': IMAGESDICT['ugly tree']}
    
        # PLAYERIMAGES is a list of all possible characters the player can be.
        # currentImage is the index of the player's current player image.
        currentImage = 0
        PLAYERIMAGES = [IMAGESDICT['princess'],
                        IMAGESDICT['boy'],
                        IMAGESDICT['catgirl'],
                        IMAGESDICT['horngirl'],
                        IMAGESDICT['pinkgirl']]
    
        startScreen() # show the title screen until the user presses a key
    
        # Read in the levels from the text file. See the readLevelsFile() for
        # details on the format of this file and how to make your own levels.
        levels = readLevelsFile('starPusherLevels.txt')
        currentLevelIndex = 0
    
        # The main game loop. This loop runs a single level, when the user
        # finishes that level, the next/previous level is loaded.
        while True: # main game loop
            # Run the level to actually start playing the game:
            result = runLevel(levels, currentLevelIndex)
    
            if result in ('solved', 'next'):
                # Go to the next level.
                currentLevelIndex += 1
                if currentLevelIndex >= len(levels):
                    # If there are no more levels, go back to the first one.
                    currentLevelIndex = 0
            elif result == 'back':
                # Go to the previous level.
                currentLevelIndex -= 1
                if currentLevelIndex < 0:
                    # If there are no previous levels, go to the last one.
                    currentLevelIndex = len(levels)-1
            elif result == 'reset':
                pass # Do nothing. Loop re-calls runLevel() to reset the level
    
    
    def runLevel(levels, levelNum):
        global currentImage
        levelObj = levels[levelNum]
        mapObj = decorateMap(levelObj['mapObj'], levelObj['startState']['player'])
        gameStateObj = copy.deepcopy(levelObj['startState'])
        mapNeedsRedraw = True # set to True to call drawMap()
        levelSurf = BASICFONT.render('Level %s of %s' % (levelNum + 1, len(levels)), 1, TEXTCOLOR)
        levelRect = levelSurf.get_rect()
        levelRect.bottomleft = (20, WINHEIGHT - 35)
        mapWidth = len(mapObj) * TILEWIDTH
        mapHeight = (len(mapObj[0]) - 1) * TILEFLOORHEIGHT + TILEHEIGHT
        MAX_CAM_X_PAN = abs(HALF_WINHEIGHT - int(mapHeight / 2)) + TILEWIDTH
        MAX_CAM_Y_PAN = abs(HALF_WINWIDTH - int(mapWidth / 2)) + TILEHEIGHT
    
        levelIsComplete = False
        # Track how much the camera has moved:
        cameraOffsetX = 0
        cameraOffsetY = 0
        # Track if the keys to move the camera are being held down:
        cameraUp = False
        cameraDown = False
        cameraLeft = False
        cameraRight = False
    
        while True: # main game loop
            # Reset these variables:
            playerMoveTo = None
            keyPressed = False
    
            for event in pygame.event.get(): # event handling loop
                if event.type == QUIT:
                    # Player clicked the "X" at the corner of the window.
                    terminate()
    
                elif event.type == KEYDOWN:
                    # Handle key presses
                    keyPressed = True
                    if event.key == K_LEFT:
                        playerMoveTo = LEFT
                    elif event.key == K_RIGHT:
                        playerMoveTo = RIGHT
                    elif event.key == K_UP:
                        playerMoveTo = UP
                    elif event.key == K_DOWN:
                        playerMoveTo = DOWN
    
                    # Set the camera move mode.
                    elif event.key == K_a:
                        cameraLeft = True
                    elif event.key == K_d:
                        cameraRight = True
                    elif event.key == K_w:
                        cameraUp = True
                    elif event.key == K_s:
                        cameraDown = True
    
                    elif event.key == K_n:
                        return 'next'
                    elif event.key == K_b:
                        return 'back'
    
                    elif event.key == K_ESCAPE:
                        terminate() # Esc key quits.
                    elif event.key == K_BACKSPACE:
                        return 'reset' # Reset the level.
                    elif event.key == K_p:
                        # Change the player image to the next one.
                        currentImage += 1
                        if currentImage >= len(PLAYERIMAGES):
                            # After the last player image, use the first one.
                            currentImage = 0
                        mapNeedsRedraw = True
    
                elif event.type == KEYUP:
                    # Unset the camera move mode.
                    if event.key == K_a:
                        cameraLeft = False
                    elif event.key == K_d:
                        cameraRight = False
                    elif event.key == K_w:
                        cameraUp = False
                    elif event.key == K_s:
                        cameraDown = False
    
            if playerMoveTo != None and not levelIsComplete:
                # If the player pushed a key to move, make the move
                # (if possible) and push any stars that are pushable.
                moved = makeMove(mapObj, gameStateObj, playerMoveTo)
    
                if moved:
                    # increment the step counter.
                    gameStateObj['stepCounter'] += 1
                    mapNeedsRedraw = True
    
                if isLevelFinished(levelObj, gameStateObj):
                    # level is solved, we should show the "Solved!" image.
                    levelIsComplete = True
                    keyPressed = False
    
            DISPLAYSURF.fill(BGCOLOR)
    
            if mapNeedsRedraw:
                mapSurf = drawMap(mapObj, gameStateObj, levelObj['goals'])
                mapNeedsRedraw = False
    
            if cameraUp and cameraOffsetY < MAX_CAM_X_PAN:
                cameraOffsetY += CAM_MOVE_SPEED
            elif cameraDown and cameraOffsetY > -MAX_CAM_X_PAN:
                cameraOffsetY -= CAM_MOVE_SPEED
            if cameraLeft and cameraOffsetX < MAX_CAM_Y_PAN:
                cameraOffsetX += CAM_MOVE_SPEED
            elif cameraRight and cameraOffsetX > -MAX_CAM_Y_PAN:
                cameraOffsetX -= CAM_MOVE_SPEED
    
            # Adjust mapSurf's Rect object based on the camera offset.
            mapSurfRect = mapSurf.get_rect()
            mapSurfRect.center = (HALF_WINWIDTH + cameraOffsetX, HALF_WINHEIGHT + cameraOffsetY)
    
            # Draw mapSurf to the DISPLAYSURF Surface object.
            DISPLAYSURF.blit(mapSurf, mapSurfRect)
    
            DISPLAYSURF.blit(levelSurf, levelRect)
            stepSurf = BASICFONT.render('Steps: %s' % (gameStateObj['stepCounter']), 1, TEXTCOLOR)
            stepRect = stepSurf.get_rect()
            stepRect.bottomleft = (20, WINHEIGHT - 10)
            DISPLAYSURF.blit(stepSurf, stepRect)
    
            if levelIsComplete:
                # is solved, show the "Solved!" image until the player
                # has pressed a key.
                solvedRect = IMAGESDICT['solved'].get_rect()
                solvedRect.center = (HALF_WINWIDTH, HALF_WINHEIGHT)
                DISPLAYSURF.blit(IMAGESDICT['solved'], solvedRect)
    
                if keyPressed:
                    return 'solved'
    
            pygame.display.update() # draw DISPLAYSURF to the screen.
            FPSCLOCK.tick()
    
    
    def isWall(mapObj, x, y):
        """Returns True if the (x, y) position on
        the map is a wall, otherwise return False."""
        if x < 0 or x >= len(mapObj) or y < 0 or y >= len(mapObj[x]):
            return False # x and y aren't actually on the map.
        elif mapObj[x][y] in ('#', 'x'):
            return True # wall is blocking
        return False
    
    
    def decorateMap(mapObj, startxy):
        """Makes a copy of the given map object and modifies it.
        Here is what is done to it:
            * Walls that are corners are turned into corner pieces.
            * The outside/inside floor tile distinction is made.
            * Tree/rock decorations are randomly added to the outside tiles.
    
        Returns the decorated map object."""
    
        startx, starty = startxy # Syntactic sugar
    
        # Copy the map object so we don't modify the original passed
        mapObjCopy = copy.deepcopy(mapObj)
    
        # Remove the non-wall characters from the map data
        for x in range(len(mapObjCopy)):
            for y in range(len(mapObjCopy[0])):
                if mapObjCopy[x][y] in ('$', '.', '@', '+', '*'):
                    mapObjCopy[x][y] = ' '
    
        # Flood fill to determine inside/outside floor tiles.
        floodFill(mapObjCopy, startx, starty, ' ', 'o')
    
        # Convert the adjoined walls into corner tiles.
        for x in range(len(mapObjCopy)):
            for y in range(len(mapObjCopy[0])):
    
                if mapObjCopy[x][y] == '#':
                    if (isWall(mapObjCopy, x, y-1) and isWall(mapObjCopy, x+1, y)) or \
                       (isWall(mapObjCopy, x+1, y) and isWall(mapObjCopy, x, y+1)) or \
                       (isWall(mapObjCopy, x, y+1) and isWall(mapObjCopy, x-1, y)) or \
                       (isWall(mapObjCopy, x-1, y) and isWall(mapObjCopy, x, y-1)):
                        mapObjCopy[x][y] = 'x'
    
                elif mapObjCopy[x][y] == ' ' and random.randint(0, 99) < OUTSIDE_DECORATION_PCT:
                    mapObjCopy[x][y] = random.choice(list(OUTSIDEDECOMAPPING.keys()))
    
        return mapObjCopy
    
    
    def isBlocked(mapObj, gameStateObj, x, y):
        """Returns True if the (x, y) position on the map is
        blocked by a wall or star, otherwise return False."""
    
        if isWall(mapObj, x, y):
            return True
    
        elif x < 0 or x >= len(mapObj) or y < 0 or y >= len(mapObj[x]):
            return True # x and y aren't actually on the map.
    
        elif (x, y) in gameStateObj['stars']:
            return True # a star is blocking
    
        return False
    
    
    def makeMove(mapObj, gameStateObj, playerMoveTo):
        """Given a map and game state object, see if it is possible for the
        player to make the given move. If it is, then change the player's
        position (and the position of any pushed star). If not, do nothing.
    
        Returns True if the player moved, otherwise False."""
    
        # Make sure the player can move in the direction they want.
        playerx, playery = gameStateObj['player']
    
        # This variable is "syntactic sugar". Typing "stars" is more
        # readable than typing "gameStateObj['stars']" in our code.
        stars = gameStateObj['stars']
    
        # The code for handling each of the directions is so similar aside
        # from adding or subtracting 1 to the x/y coordinates. We can
        # simplify it by using the xOffset and yOffset variables.
        if playerMoveTo == UP:
            xOffset = 0
            yOffset = -1
        elif playerMoveTo == RIGHT:
            xOffset = 1
            yOffset = 0
        elif playerMoveTo == DOWN:
            xOffset = 0
            yOffset = 1
        elif playerMoveTo == LEFT:
            xOffset = -1
            yOffset = 0
    
        # See if the player can move in that direction.
        if isWall(mapObj, playerx + xOffset, playery + yOffset):
            return False
        else:
            if (playerx + xOffset, playery + yOffset) in stars:
                # There is a star in the way, see if the player can push it.
                if not isBlocked(mapObj, gameStateObj, playerx + (xOffset*2), playery + (yOffset*2)):
                    # Move the star.
                    ind = stars.index((playerx + xOffset, playery + yOffset))
                    stars[ind] = (stars[ind][0] + xOffset, stars[ind][1] + yOffset)
                else:
                    return False
            # Move the player upwards.
            gameStateObj['player'] = (playerx + xOffset, playery + yOffset)
            return True
    
    
    def startScreen():
        """Display the start screen (which has the title and instructions)
        until the player presses a key. Returns None."""
    
        # Position the title image.
        titleRect = IMAGESDICT['title'].get_rect()
        topCoord = 50 # topCoord tracks where to position the top of the text
        titleRect.top = topCoord
        titleRect.centerx = HALF_WINWIDTH
        topCoord += titleRect.height
    
        # Unfortunately, Pygame's font & text system only shows one line at
        # a time, so we can't use strings with \n newline characters in them.
        # So we will use a list with each line in it.
        instructionText = ['Push the stars over the marks.',
                           'Arrow keys to move, WASD for camera control, P to change character.',
                           'Backspace to reset level, Esc to quit.',
                           'N for next level, B to go back a level.']
    
        # Start with drawing a blank color to the entire window:
        DISPLAYSURF.fill(BGCOLOR)
    
        # Draw the title image to the window:
        DISPLAYSURF.blit(IMAGESDICT['title'], titleRect)
    
        # Position and draw the text.
        for i in range(len(instructionText)):
            instSurf = BASICFONT.render(instructionText[i], 1, TEXTCOLOR)
            instRect = instSurf.get_rect()
            topCoord += 10 # 10 pixels will go in between each line of text.
            instRect.top = topCoord
            instRect.centerx = HALF_WINWIDTH
            topCoord += instRect.height # Adjust for the height of the line.
            DISPLAYSURF.blit(instSurf, instRect)
    
        while True: # Main loop for the start screen.
            for event in pygame.event.get():
                if event.type == QUIT:
                    terminate()
                elif event.type == KEYDOWN:
                    if event.key == K_ESCAPE:
                        terminate()
                    return # user has pressed a key, so return.
    
            # Display the DISPLAYSURF contents to the actual screen.
            pygame.display.update()
            FPSCLOCK.tick()
    
    
    def readLevelsFile(filename):
        assert os.path.exists(filename), 'Cannot find the level file: %s' % (filename)
        mapFile = open(filename, 'r')
        # Each level must end with a blank line
        content = mapFile.readlines() + ['\r\n']
        mapFile.close()
    
        levels = [] # Will contain a list of level objects.
        levelNum = 0
        mapTextLines = [] # contains the lines for a single level's map.
        mapObj = [] # the map object made from the data in mapTextLines
        for lineNum in range(len(content)):
            # Process each line that was in the level file.
            line = content[lineNum].rstrip('\r\n')
    
            if ';' in line:
                # Ignore the ; lines, they're comments in the level file.
                line = line[:line.find(';')]
    
            if line != '':
                # This line is part of the map.
                mapTextLines.append(line)
            elif line == '' and len(mapTextLines) > 0:
                # A blank line indicates the end of a level's map in the file.
                # Convert the text in mapTextLines into a level object.
    
                # Find the longest row in the map.
                maxWidth = -1
                for i in range(len(mapTextLines)):
                    if len(mapTextLines[i]) > maxWidth:
                        maxWidth = len(mapTextLines[i])
                # Add spaces to the ends of the shorter rows. This
                # ensures the map will be rectangular.
                for i in range(len(mapTextLines)):
                    mapTextLines[i] += ' ' * (maxWidth - len(mapTextLines[i]))
    
                # Convert mapTextLines to a map object.
                for x in range(len(mapTextLines[0])):
                    mapObj.append([])
                for y in range(len(mapTextLines)):
                    for x in range(maxWidth):
                        mapObj[x].append(mapTextLines[y][x])
    
                # Loop through the spaces in the map and find the @, ., and $
                # characters for the starting game state.
                startx = None # The x and y for the player's starting position
                starty = None
                goals = [] # list of (x, y) tuples for each goal.
                stars = [] # list of (x, y) for each star's starting position.
                for x in range(maxWidth):
                    for y in range(len(mapObj[x])):
                        if mapObj[x][y] in ('@', '+'):
                            # '@' is player, '+' is player & goal
                            startx = x
                            starty = y
                        if mapObj[x][y] in ('.', '+', '*'):
                            # '.' is goal, '*' is star & goal
                            goals.append((x, y))
                        if mapObj[x][y] in ('$', '*'):
                            # '$' is star
                            stars.append((x, y))
    
                # Basic level design sanity checks:
                assert startx != None and starty != None, 'Level %s (around line %s) in %s is missing a "@" or "+" to mark the start point.' % (levelNum+1, lineNum, filename)
                assert len(goals) > 0, 'Level %s (around line %s) in %s must have at least one goal.' % (levelNum+1, lineNum, filename)
                assert len(stars) >= len(goals), 'Level %s (around line %s) in %s is impossible to solve. It has %s goals but only %s stars.' % (levelNum+1, lineNum, filename, len(goals), len(stars))
    
                # Create level object and starting game state object.
                gameStateObj = {'player': (startx, starty),
                                'stepCounter': 0,
                                'stars': stars}
                levelObj = {'width': maxWidth,
                            'height': len(mapObj),
                            'mapObj': mapObj,
                            'goals': goals,
                            'startState': gameStateObj}
    
                levels.append(levelObj)
    
                # Reset the variables for reading the next map.
                mapTextLines = []
                mapObj = []
                gameStateObj = {}
                levelNum += 1
        return levels
    
    
    def floodFill(mapObj, x, y, oldCharacter, newCharacter):
        """Changes any values matching oldCharacter on the map object to
        newCharacter at the (x, y) position, and does the same for the
        positions to the left, right, down, and up of (x, y), recursively."""
    
        # In this game, the flood fill algorithm creates the inside/outside
        # floor distinction. This is a "recursive" function.
        # For more info on the Flood Fill algorithm, see:
        #   http://en.Wikipedia.org/wiki/Flood_fill
        if mapObj[x][y] == oldCharacter:
            mapObj[x][y] = newCharacter
    
        if x < len(mapObj) - 1 and mapObj[x+1][y] == oldCharacter:
            floodFill(mapObj, x+1, y, oldCharacter, newCharacter) # call right
        if x > 0 and mapObj[x-1][y] == oldCharacter:
            floodFill(mapObj, x-1, y, oldCharacter, newCharacter) # call left
        if y < len(mapObj[x]) - 1 and mapObj[x][y+1] == oldCharacter:
            floodFill(mapObj, x, y+1, oldCharacter, newCharacter) # call down
        if y > 0 and mapObj[x][y-1] == oldCharacter:
            floodFill(mapObj, x, y-1, oldCharacter, newCharacter) # call up
    
    
    def drawMap(mapObj, gameStateObj, goals):
        """Draws the map to a Surface object, including the player and
        stars. This function does not call pygame.display.update(), nor
        does it draw the "Level" and "Steps" text in the corner."""
    
        # mapSurf will be the single Surface object that the tiles are drawn
        # on, so that it is easy to position the entire map on the DISPLAYSURF
        # Surface object. First, the width and height must be calculated.
        mapSurfWidth = len(mapObj) * TILEWIDTH
        mapSurfHeight = (len(mapObj[0]) - 1) * TILEFLOORHEIGHT + TILEHEIGHT
        mapSurf = pygame.Surface((mapSurfWidth, mapSurfHeight))
        mapSurf.fill(BGCOLOR) # start with a blank color on the surface.
    
        # Draw the tile sprites onto this surface.
        for x in range(len(mapObj)):
            for y in range(len(mapObj[x])):
                spaceRect = pygame.Rect((x * TILEWIDTH, y * TILEFLOORHEIGHT, TILEWIDTH, TILEHEIGHT))
                if mapObj[x][y] in TILEMAPPING:
                    baseTile = TILEMAPPING[mapObj[x][y]]
                elif mapObj[x][y] in OUTSIDEDECOMAPPING:
                    baseTile = TILEMAPPING[' ']
    
                # First draw the base ground/wall tile.
                mapSurf.blit(baseTile, spaceRect)
    
                if mapObj[x][y] in OUTSIDEDECOMAPPING:
                    # Draw any tree/rock decorations that are on this tile.
                    mapSurf.blit(OUTSIDEDECOMAPPING[mapObj[x][y]], spaceRect)
                elif (x, y) in gameStateObj['stars']:
                    if (x, y) in goals:
                        # A goal AND star are on this space, draw goal first.
                        mapSurf.blit(IMAGESDICT['covered goal'], spaceRect)
                    # Then draw the star sprite.
                    mapSurf.blit(IMAGESDICT['star'], spaceRect)
                elif (x, y) in goals:
                    # Draw a goal without a star on it.
                    mapSurf.blit(IMAGESDICT['uncovered goal'], spaceRect)
    
                # Last draw the player on the board.
                if (x, y) == gameStateObj['player']:
                    # Note: The value "currentImage" refers
                    # to a key in "PLAYERIMAGES" which has the
                    # specific player image we want to show.
                    mapSurf.blit(PLAYERIMAGES[currentImage], spaceRect)
    
        return mapSurf
    
    
    def isLevelFinished(levelObj, gameStateObj):
        """Returns True if all the goals have stars in them."""
        for goal in levelObj['goals']:
            if goal not in gameStateObj['stars']:
                # Found a space with a goal but no star on it.
                return False
        return True
    
    
    def terminate():
        pygame.quit()
        sys.exit()
    
    
    if __name__ == '__main__':
        main()
    

    This page titled 10.2: Source Code to Star Pusher is shared under a CC BY-NC-SA 3.0 license and was authored, remixed, and/or curated by Al Sweigart via source content that was edited to the style and standards of the LibreTexts platform.

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