Boxxle in Haskell + SDL


Haskell || Die

The main driver for me studying programming in the first place was because I love programming video games. After the discovery of SDL bindings for Haskell, along with an amazing tutorial, I couldn't resist trying to make a simple game in Haskell. It took a lottttttt of reading and time in GHCI before I could start making any real progress, but after a couple days I began to wrap my head around things. This is a small remake of the GameBoy game Boxxle, a very simple but fun puzzle game.

The full code (with 40 levels) can be found on my GitHub

Below is the current version. I am still wrapping my head around the intricacies of Haskell, so feel free to make suggestions :)

Boxxle.hs

{-# LANGUAGE FlexibleContexts #-} -- http://stackoverflow.com/questions/10865963/using-the-state-monad-to-hide-explicit-state

-- @author Kenny Cason
-- kennycason.com 2013

import Graphics.UI.SDL
import Graphics.UI.SDL.TTF as TTFG
import Graphics.UI.SDL.Mixer

import Data.List

import Control.Monad
import Control.Monad.State
import Control.Monad.Reader

import Timer

-- game data
-- levels from: http://www.gamefaqs.com/gameboy/585643-boxxle/faqs/52416

rooms = [
    roomBuilder
        [[1,1,1,1,1,0,0,0,0]                    -- map tiles
        ,[1,0,0,0,1,0,0,0,0]
        ,[1,0,0,0,1,0,1,1,1]
        ,[1,0,0,0,1,0,1,4,1]
        ,[1,1,1,0,1,1,1,4,1]
        ,[0,1,1,0,0,0,0,4,1]
        ,[0,1,0,0,0,1,0,0,1]
        ,[0,1,0,0,0,1,1,1,1]
        ,[0,1,1,1,1,1,0,0,0]
        ]
        [(Coord 2 2), (Coord 3 2), (Coord 2 3)] -- boxes
        [(Coord 7 3), (Coord 7 4), (Coord 7 5)] -- targets
        (Coord 1 1)                                -- start pos
    ,roomBuilder
        [[1,1,1,1,1,1,1,1,1,1]
        ,[1,4,4,0,0,0,0,0,0,1]
        ,[1,4,4,0,0,0,1,0,0,1]
        ,[1,0,0,1,0,1,1,0,1,1]
        ,[1,0,0,0,0,0,0,0,1,0]
        ,[1,1,1,1,1,0,1,0,1,0]
        ,[0,0,1,0,0,0,0,0,1,0]
        ,[0,0,1,0,0,0,0,0,1,0]
        ,[0,0,1,1,1,1,1,1,1,0]
        ]
        [(Coord 3 2), (Coord 4 3), (Coord 2 4), (Coord 4 6)]
        [(Coord 1 1), (Coord 2 1), (Coord 1 2), (Coord 2 2)]
        (Coord 1 1)
    ,roomBuilder
        [[0,1,1,1,1,0]
        ,[1,1,0,0,1,0]
        ,[1,0,0,0,1,0]
        ,[1,1,0,0,1,1]
        ,[1,1,0,0,0,1]
        ,[1,4,0,0,0,1]
        ,[1,4,4,0,4,1]
        ,[1,1,1,1,1,1]
        ]
        [(Coord 2 2), (Coord 2 3), (Coord 3 4), (Coord 2 5)]
        [(Coord 1 5), (Coord 1 6), (Coord 2 6), (Coord 4 6)]
        (Coord 1 2)
    ,roomBuilder
        [[0,1,1,1,1,1,0,0]
        ,[0,1,0,0,1,1,1,0]
        ,[0,1,0,0,0,0,1,0]
        ,[1,1,1,0,1,0,1,1]
        ,[1,4,1,0,1,0,0,1]
        ,[1,4,0,0,0,1,0,1]
        ,[1,4,0,0,0,0,0,1]
        ,[1,1,1,1,1,1,1,1]
        ]
        [(Coord 3 2), (Coord 2 5), (Coord 5 6)]
        [(Coord 1 4), (Coord 1 5), (Coord 1 6)]
        (Coord 2 1)
    ,roomBuilder
        [[0,1,1,1,1,1,1,1,0,0]
        ,[0,1,0,0,0,0,0,1,1,1]
        ,[1,1,0,1,1,1,0,0,0,1]
        ,[1,0,0,0,0,0,0,0,0,1]
        ,[1,0,4,4,1,0,0,0,1,1]
        ,[1,1,4,4,1,0,0,0,1,0]
        ,[0,1,1,1,1,1,1,1,1,0]
        ]
        [(Coord 2 2), (Coord 4 3), (Coord 6 3), (Coord 5 4)]
        [(Coord 2 4), (Coord 3 4), (Coord 2 5), (Coord 3 5)]
        (Coord 2 1)
    ]

roomBuilder ::[[Int]] -> [Coord] -> [Coord] -> Coord -> Room
roomBuilder tiles boxes targets startPos = Room {
        tiles = tiles
        ,walls = foldTiles tiles
        ,boxes = boxes
        ,targets = targets
        ,startPos = startPos
    }


-- global constants
startLevel = 1

tEmpty     = 0
tBrick     = 1
tBox     = 2
tPlayer = 3
tTarget    = 4

textColor = Color 0x33 0x33 0x33


-- type defines
data Direction = UP | DOWN | LEFT | RIGHT deriving (Eq, Enum)

data Move = Move {
    dir :: Direction
    ,dx :: Int
    ,dy :: Int
}

data Coord = Coord {
    x :: Int
    ,y :: Int
} deriving (Eq)

data Room = Room {
    tiles :: [[Int]]
    ,walls :: [Coord]
    ,boxes :: [Coord]
    ,targets :: [Coord]
    ,startPos :: Coord
}

data GameData = GameData {
    timer :: Timer
    ,room :: Room
    ,player :: Coord
    ,level :: Int
}        

data GameConfig = GameConfig {
    screen :: Surface
    ,sprites :: Surface
    ,front :: Font
    ,music :: Music
}

type GameState = StateT GameData IO
type GameEnv = ReaderT GameConfig GameState


-- monad state get/put/modify
getGameData :: MonadState GameData m => m GameData
getGameData = get

putGameData :: MonadState GameData m => GameData -> m ()
putGameData = put

modifyGameData :: MonadState GameData m => (GameData -> GameData) -> m ()
modifyGameData = modify

getPlayer :: MonadState GameData m => m Coord
getPlayer = gets player

getRoom :: MonadState GameData m => m Room
getRoom = gets room

getLevel :: MonadState GameData m => m Int
getLevel = gets level

getTimer :: MonadState GameData m => m Timer
getTimer = gets timer

putTimer :: MonadState GameData m => Timer -> m ()
putTimer t = modify $ \s -> s { timer = t }

modifyTimerM :: MonadState GameData m => (Timer -> m Timer) -> m ()
modifyTimerM act = getTimer >>= act >>= putTimer

getScreen :: MonadReader GameConfig m => m Surface
getScreen = liftM screen ask

getSprites :: MonadReader GameConfig m => m Surface
getSprites = liftM sprites ask

getFont :: MonadReader GameConfig m => m Font
getFont = liftM front ask


-- main functions
newGame :: Int -> IO (GameConfig, GameData)
newGame lvl = do
    -- setVideoMode 320 288 32 []
    setVideoMode 448 352 32 []
    setCaption "Boxxle - Haskell" []
    screen  <- getVideoSurface
    sprites <- loadBMP "img/boxxle.bmp"
    font    <- openFont "fonts/steelpla.ttf" 18
    timer   <- start defaultTimer

    openAudio 22050 AudioS16Sys 2 4096
    music   <- loadMUS "music/main.wav"
    playMusic music (-1)
    return (GameConfig screen sprites font music, GameData timer room (startPos room) lvl)
    where room = (rooms !! (lvl - 1))


levelUp :: GameData -> GameData
levelUp gd = gd { level = newLevel, room = nextRoom, player = (startPos nextRoom) }
            where
                newLevel = (level gd) + 1
                nextRoom = rooms !! ((level gd) `mod` (length rooms))


resetLevel :: GameData -> GameData
resetLevel gd = gd { room = resetRoom, player = (startPos resetRoom) }
                where resetRoom = rooms !! ( ((level gd) - 1) `mod` (length rooms) )


handleWin :: GameData -> GameData
handleWin gd| isWin = levelUp gd
            | otherwise = gd
                where isWin = length (intersect
                                        (boxes currentRoom)
                                        (targets currentRoom)) == length (targets currentRoom)
                                            where currentRoom = (room gd)


foldTiles :: [[Int]] -> [Coord]
foldTiles tiles =
  [Coord x y                         -- generate a Coord pair
    | (y, row) <- enumerate tiles    -- for each row with its coordinate
    , (x, tile) <- enumerate row     -- for each tile in the row (with coordinate)
    , tile == 1]                     -- if the tile is 1
        where enumerate = zip [0..]


getSpriteSheetOffset :: Int -> Maybe Rect
getSpriteSheetOffset n = Just (Rect offx offy 32 32)
                            where
                                offx = n * 32
                                offy = 0


applySurface :: Int -> Int -> Surface -> Surface -> Maybe Rect -> IO Bool
applySurface x y src dst clip = blitSurface src clip dst offset
    where offset = Just Rect { rectX = x, rectY = y, rectW = 0, rectH = 0 }


drawSprite :: Surface -> Surface -> Int -> Int -> Int -> IO Bool
drawSprite screen sprites n x y = blitSurface
                                        sprites (getSpriteSheetOffset n)
                                        screen dst
                                            where dst = Just (Rect x y 32 32)


drawPlayer :: Surface -> Surface -> Int -> Int -> IO Bool
drawPlayer screen sprites x y = blitSurface sprites src screen dst
                                where
                                    src = (getSpriteSheetOffset tPlayer)
                                    dst = Just (Rect (x * 32) (y * 32) 32 32)


drawTile :: Surface -> Surface -> Int -> [Coord] -> IO()
drawTile screen sprites tile coords = mapM_ (\c -> drawSprite screen sprites tile ((x c) * 32) ((y c) * 32) ) coords


drawBricks :: Surface -> Surface -> [Coord] -> IO()
drawBricks screen sprites bricks = drawTile screen sprites tBrick bricks


drawBoxes :: Surface -> Surface -> [Coord] -> IO()
drawBoxes screen sprites boxes = drawTile screen sprites tBox boxes


drawTargets :: Surface -> Surface -> [Coord] -> IO()
drawTargets screen sprites targets = drawTile screen sprites tTarget targets


collide :: Coord -> Coord -> Bool
collide c1 c2 = ((x c1) == (x c2)) && ((y c1) == (y c2))


offsetCoord :: Coord -> Move -> Coord
offsetCoord c move = c { x = (x c) + (dx move), y = (y c) + (dy move) }


collideWithWorld :: Coord -> Room -> Bool
collideWithWorld c room = (foldr (||) False (map (collide c) (walls room)))


collideWithBoxes :: Coord -> Room -> Bool
collideWithBoxes c room = (foldr (||) False (map (collide c) (boxes room)))    


canBoxMove :: Coord -> Room -> Bool            
canBoxMove box room = not ((collideWithWorld box room) || (collideWithBoxes box room))


movePlayer :: Move -> GameData -> GameData
movePlayer move gd     | collideWithWorld newPlayerPos (room gd) = gd
                    | otherwise = gd { player = Coord { x = (x playerPos) + (dx move), y = (y playerPos) + (dy move)} }
                    where
                        playerPos = (player gd)
                        newPlayerPos = (offsetCoord playerPos move)


moveBox :: Move -> Coord -> Coord
moveBox move box = box { x = (x box) + (dx move), y = (y box) + (dy move) }


checkBox :: Room -> Coord -> Move -> Coord -> Coord
checkBox room playerPos move box| collidedWithPlayer && (dir move) == UP && boxCanMove = moveBox move box
                                | collidedWithPlayer && (dir move) == DOWN && boxCanMove = moveBox move box
                                | collidedWithPlayer && (dir move) == LEFT && boxCanMove = moveBox move box
                                | collidedWithPlayer && (dir move) == RIGHT && boxCanMove = moveBox move box
                                | otherwise = box
                                    where
                                        collidedWithPlayer = collide playerPos box -- player collided
                                        boxCanMove = canBoxMove newBoxPos room
                                            where newBoxPos = offsetCoord box move


checkBoxes :: Room -> Coord -> Move -> [Coord] -> [Coord]
checkBoxes room playerPos move boxes = map (checkBox room playerPos move) boxes


handleBoxes :: Move -> GameData -> GameData
handleBoxes move gd = gd { room = (room gd) { boxes = (checkBoxes (room gd) playerPos move (boxes (room gd)) ) } }
                        where playerPos = offsetCoord (player gd) move


-- if the resulting move yields the player standing on a box, undo it
undoPlayer :: Move -> GameData -> GameData
undoPlayer move gd     | collideWithBoxes playerPos (room gd) = gd { player = Coord { x = (x playerPos) - (dx move), y = (y playerPos) - (dy move)} }
                    | otherwise = gd
                    where
                        playerPos = (player gd)


handleKeyboard :: Event -> GameData -> GameData
handleKeyboard (KeyDown (Keysym SDLK_UP _ _)) gd = ((handleWin.undoPlayer move).(movePlayer move).(handleBoxes move)) gd
                                                    where move = Move { dir = UP, dx = 0, dy = -1 }
handleKeyboard (KeyDown (Keysym SDLK_DOWN _ _)) gd = ((handleWin.undoPlayer move).(movePlayer move).(handleBoxes move)) gd
                                                    where move = Move { dir = DOWN, dx = 0, dy = 1 }
handleKeyboard (KeyDown (Keysym SDLK_LEFT _ _)) gd = ((handleWin.undoPlayer move).(movePlayer move).(handleBoxes move)) gd
                                                    where move = Move { dir = LEFT, dx = -1, dy = 0 }
handleKeyboard (KeyDown (Keysym SDLK_RIGHT _ _)) gd = ((handleWin.undoPlayer move).(movePlayer move).(handleBoxes move))  gd
                                                    where move = Move { dir = RIGHT, dx = 1, dy = 0 }
handleKeyboard (KeyDown (Keysym SDLK_r _ _)) gd = resetLevel gd
handleKeyboard (KeyDown (Keysym SDLK_s _ _)) gd = levelUp gd
handleKeyboard _ d = d


loop :: GameEnv ()
loop = do
    timer   <- getTimer
    screen  <- getScreen
    sprites <- getSprites
    pos     <- getPlayer
    room    <- getRoom
    font    <- getFont
    level   <- getLevel
    message <- liftIO $ renderTextSolid font ("level " ++ (show level)) textColor

    modifyTimerM $ liftIO . start
    quit <- whileEvents $ modifyGameData . handleKeyboard

    liftIO $ do
        bgRect    <- Just `liftM` getClipRect screen
        white     <- mapRGB' screen 0xff 0xff 0xff
        fillRect screen bgRect white

        drawBricks screen sprites (walls room)
        drawTargets screen sprites (targets room)
        drawBoxes screen sprites (boxes room)
        drawPlayer screen sprites (x pos) (y pos)

        applySurface 340 3 message screen Nothing

        Graphics.UI.SDL.flip screen

        ticks <- getTimerTicks timer
        when (ticks < secsPerFrame) $ do
            delay $ secsPerFrame - ticks
    unless quit loop
 where
    framesPerSecond = 30
    secsPerFrame = 1000 `div` framesPerSecond
    mapRGB' = mapRGB . surfaceGetPixelFormat


whileEvents :: MonadIO m => (Event -> m ()) -> m Bool
whileEvents act = do
    event <- liftIO pollEvent
    case event of
        Quit -> return True
        NoEvent -> return False
        _ -> do
            act event
            whileEvents act


runLoop :: GameConfig -> GameData -> IO ()
runLoop = evalStateT . runReaderT loop


main = withInit [InitEverything] $ do -- withInit calls quit
    result <- TTFG.init
    if not result
        then putStr "Failed to init ttf\n"
        else do
            (gc, gd) <- newGame startLevel
            runLoop gc gd
            haltMusic
            closeAudio
            TTFG.quit

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