diff --git a/vm/Datatypes.hs b/vm/Datatypes.hs
new file mode 100644
index 0000000..da4d1cc
--- /dev/null
+++ b/vm/Datatypes.hs
@@ -0,0 +1,47 @@
+module Datatypes where
+
+import Data.Hashable (Hashable(..))
+import qualified Data.List as List
+import Data.Set (Set)
+import qualified Data.Set as Set
+
+type Cell = (Int, Int)
+
+data Board = Board {
+           boardWidth :: Int,
+           boardHeight :: Int,
+           boardFilled :: Set Cell
+           }
+           deriving Show
+
+data Unit = Unit {
+          unitMembers :: Set Cell,
+          unitPivot :: Cell
+          }
+          deriving Show
+
+data Command = MoveW
+             | MoveE
+             | MoveSW
+             | MoveSE
+             | RotateClockwise
+             | RotateCounterclockwise
+             deriving Show
+
+data Game = Game {
+          gameBoard :: Board,
+          gameUnits :: [Unit],
+          oldPositions :: Set Int
+          }
+          deriving Show
+
+data Notes = OK
+           | Ended
+           | Collision
+           | CollisionWithRowElision
+           | ErrorZero
+           deriving Show
+
+instance Hashable Unit where
+        hashWithSalt salt (Unit members pivot) =
+            hashWithSalt salt (List.sort (Set.toList members), pivot)
diff --git a/vm/Tests.hs b/vm/Tests.hs
index 77bb38e..84c1d8d 100644
--- a/vm/Tests.hs
+++ b/vm/Tests.hs
@@ -1,3 +1,4 @@
+import Datatypes
 import VM
 
 import Data.Hashable (hash, Hashable(..))
@@ -46,5 +47,5 @@ testControRotazioni :: Cell -> [Cell] -> Maybe Cell
 testControRotazioni _ [] = Nothing
 testControRotazioni _ [x] = Nothing
 testControRotazioni pivot (x:y:xs) = if counterRotateCell pivot x == y
-                                   then testRotazioni pivot (y:xs)
+                                   then testControRotazioni pivot (y:xs)
                                    else Just x
diff --git a/vm/VM.hs b/vm/VM.hs
index 5e7c070..2cbaff7 100644
--- a/vm/VM.hs
+++ b/vm/VM.hs
@@ -5,50 +5,10 @@ import qualified Data.List as List
 import Data.Set (Set)
 import qualified Data.Set as Set
 
-type Cell = (Int, Int)
-
-data Board = Board {
-           boardWidth :: Int,
-           boardHeight :: Int,
-           filled :: Set Cell
-           }
-           deriving Show
-
-data Unit = Unit {
-          unitMembers :: Set Cell,
-          unitPivot :: Cell
-          }
-          deriving Show
-
-data Command = MoveW
-             | MoveE
-             | MoveSW
-             | MoveSE
-             | RotateClockwise
-             | RotateCounterclockwise
-             deriving Show
-
-
-data Game = Game {
-          gameBoard :: Board,
-          gameUnits :: [Unit],
-          oldPositions :: Set Int
-          }
-          deriving Show
-
-instance Hashable Unit where
-        hashWithSalt salt (Unit members pivot) =
-            hashWithSalt salt (List.sort (Set.toList members), pivot)
-
-data Notes = OK
-           | Ended
-           | Collision
-           | CollisionWithRowElision
-           | ErrorZero
-           deriving Show
+import Datatypes
 
 collides :: Unit -> Board -> Bool
-collides u b = not . Set.null $ Set.intersection (unitMembers u) (filled b)
+collides u b = not . Set.null $ Set.intersection (unitMembers u) (boardFilled b)
 
 isInvalidFor :: Unit -> Board -> Bool
 isInvalidFor u b = any isOutside (Set.toList $ unitMembers u) where
@@ -56,7 +16,7 @@ isInvalidFor u b = any isOutside (Set.toList $ unitMembers u) where
 
 lockUnit :: Game -> Game
 lockUnit (Game board (u:us) _) = Game newBoard us (Set.fromList []) where
-    newBoard = board { filled = Set.union (unitMembers u) (filled board) }
+    newBoard = board { boardFilled = Set.union (unitMembers u) (boardFilled board) }
 
 checkSpawn :: Game -> Game
 checkSpawn game@(Game _ [] _) = game