diff --git a/src/Direction.elm b/src/Direction.elm
index ccbd5de..3e46c92 100644
--- a/src/Direction.elm
+++ b/src/Direction.elm
@@ -1,4 +1,4 @@
-module Direction exposing (Direction, down, left, move, right, up)
+module Direction exposing (Direction, down, left, move, opposite, right, up)
 
 
 type alias Direction =
@@ -25,6 +25,11 @@ right =
     ( 0, 1 )
 
 
+opposite : Direction -> Direction
+opposite ( row, column ) =
+    ( -row, -column )
+
+
 move : { row : Int, column : Int } -> Direction -> { row : Int, column : Int }
 move { row, column } ( adjRow, adjCol ) =
     { row = row + adjRow