example from https://tarquin-the-brave.github.io/blog/posts/re-learning-haskell-2/

playgame.hs

data LiveData = LiveData {
  -- x-coordinate of the ball - xb
  xb::Int,
  -- x-coordinate of the paddle - xp
  xp::Int,
  -- Game score - sc
  sc::Int
} deriving(Show)

stepGame' :: [Int] -> Game -> (LiveData, Game)

stepGame :: [Int] -> State Game LiveData
stepGame = state . stepGame'

playGame :: [Int] -> State Game Int
playGame inp = do
  liveData <- stepGame inp
  game <- get
  case IC.progState (gameProg game) of
    IC.AwaitInput -> playGame [joystick (xb liveData) (xp liveData)]
    _ -> return $ sc liveData

joystick :: Int -> Int -> Int