Hello, You have this type error: Couldn't match expected type ‘StateT StdGen Data.Functor.Identity.Identity Integer’ with actual type ‘g1 -> (Integer, g1)’ It's because you're trying to use a `(s -> (a,s))` function "unwrapped" where GHC expects it "wrapped" in a StateT. The type of `state` from Control.Monad.State (mtl package) is: state :: (s -> (a, s)) -> m a so it could solve your mismatch, turning `g1 -> (Integer, g1)` into `StateT StdGen Identity Integer`, like: np <- state (randomR (1, maxRandPlayers)) Alternatively, if you don't want to use mtl, you can use `StateT`s constructor directly. It's type is: StateT :: (s -> m (a, s)) -> StateT s m a so you'd have to compose `randomR` with `return` (or `pure`) first: np <- StateT (return . randomR (1, maxRandPlayers)) Best regards, Marcin Mrotek