-- returns the floor items of the given floor
getFloorItems' :: State -> Int -> ItemSet
getFloorItems' (State _ v) f =
    fromIntegral $ v `unsafeShiftR` (f * stateFloorSize) .&. stateFloorMask
getFloorItems' :: State -> Int -> ItemSet
getFloorItems' (State _ v) f =
    fromIntegral $ v `unsafeShiftR` (f * stateFloorSize) .&. stateFloorMask
getFloorItems' (State _ v) f =
    fromIntegral $ v `unsafeShiftR` (f * stateFloorSize) .&. stateFloorMask