diff --git a/Internal/World.hs b/Internal/World.hs
index 5e37973..08bb6d1 100644
--- a/Internal/World.hs
+++ b/Internal/World.hs
@@ -1,7 +1,7 @@
 {-# LANGUAGE LambdaCase #-}
 
 module Internal.World
-  ( World,
+  ( World(..),
     worldWithDimensions,
     getBeepersAt,
     setBeepersAt,
@@ -70,29 +70,29 @@ addWallAt :: Vector -> Direction -> World -> World
 addWallAt pos dir w
   | not $ positionWithinWorld w newPosition = error "Invalid position"
   | isOnEdge (worldDimensions w) newPosition newDirection = w
-  | otherwise = w {worldWalls = M.insert pos newWalls (worldWalls w)}
+  | otherwise = w {worldWalls = M.insert newPosition newWalls (worldWalls w)}
   where
     (newPosition, newDirection) = switchDirectionToInternal pos dir
-    oldWalls = M.findWithDefault S.empty pos (worldWalls w)
-    newWalls = S.union oldWalls $ S.singleton dir
+    oldWalls = M.findWithDefault S.empty newPosition (worldWalls w)
+    newWalls = S.union oldWalls $ S.singleton newDirection
 
 removeWallAt :: Vector -> Direction -> World -> World
 removeWallAt pos dir w
   | not $ positionWithinWorld w newPosition = error "Invalid position"
   | isOnEdge (worldDimensions w) newPosition newDirection = w
-  | S.null newWalls = w {worldWalls = M.delete pos (worldWalls w)}
-  | otherwise = w {worldWalls = M.insert pos newWalls (worldWalls w)}
+  | S.null newWalls = w {worldWalls = M.delete newPosition (worldWalls w)}
+  | otherwise = w {worldWalls = M.insert newPosition newWalls (worldWalls w)}
   where
     (newPosition, newDirection) = switchDirectionToInternal pos dir
-    oldWalls = M.findWithDefault S.empty pos (worldWalls w)
-    newWalls = oldWalls S.\\ S.singleton dir
+    oldWalls = M.findWithDefault S.empty newPosition (worldWalls w)
+    newWalls = oldWalls S.\\ S.singleton newDirection
 
 hasWallAt :: Vector -> Direction -> World -> Bool
 hasWallAt pos dir w
   | not $ positionWithinWorld w newPosition = False
   | isOnEdge (worldDimensions w) newPosition newDirection = True
-  | otherwise = case worldWalls w M.!? pos of
-    Just wallsInPlace -> S.member dir wallsInPlace
+  | otherwise = case worldWalls w M.!? newPosition of
+    Just wallsInPlace -> S.member newDirection wallsInPlace
     Nothing -> False
   where
     (newPosition, newDirection) = switchDirectionToInternal pos dir