diff --git a/src/Hamming/App/Types.hs b/src/Hamming/App/Types.hs
index 267cf8a..e3527b0 100644
--- a/src/Hamming/App/Types.hs
+++ b/src/Hamming/App/Types.hs
@@ -30,7 +30,15 @@ module Hamming.App.Types (
   -- * AppState
   AppState (..),
   -- ** Lenses
+  appMode,
   hammingCode,
+  -- * AppMode
+  AppMode (..),
+  -- * EditState,
+  EditState (..),
+  -- ** Lenses
+  rowNum,
+  colNum,
   -- * Other Types
   ResName,
   Event,
@@ -46,7 +54,21 @@ import Lens.Micro.TH (makeLenses)
 
 -- | The main state of the application
 data AppState = AppState
-  { _hammingCode :: Word16
+  { _appMode :: AppMode
+  , _hammingCode :: Word16
+  }
+
+-- | The application's main mode
+data AppMode
+  = DisplayMode
+  | EditMode EditState
+
+-- | The state of the editor
+data EditState = EditState
+  { _rowNum :: Int
+  -- ^ The selected row number
+  , _colNum :: Int
+  -- ^ The selected column
   }
 
 -- | Identifies a resource
@@ -61,10 +83,13 @@ type Action a = EventM ResName AppState a
 -- | Event handler
 type Handler = Event -> Action ()
 
-makeLenses ''AppState
+concat <$> mapM makeLenses
+  [ ''AppState
+  , ''EditState
+  ]
 
 -- | Initial application state
 initialState :: AppState
-initialState = AppState 0
+initialState = AppState DisplayMode 0
 
 --jl
diff --git a/test/Hamming/App/Widgets/InternalSpec.hs b/test/Hamming/App/Widgets/InternalSpec.hs
index 11def99..fa893dc 100644
--- a/test/Hamming/App/Widgets/InternalSpec.hs
+++ b/test/Hamming/App/Widgets/InternalSpec.hs
@@ -44,16 +44,16 @@ hammingW'Spec = describe "hammingW'" $ mapM_
       it ("should be " ++ show numExpRows) $
         numActRows `shouldBe` numExpRows
     mapM_
-      ( \(rowNum, actRow, expRow) -> let
+      ( \(row, actRow, expRow) -> let
         numActCols = length actRow
         numExpCols = length expRow
-        in context ("row " ++ show rowNum) $ do
+        in context ("row " ++ show row) $ do
           context "number of columns" $
             it ("should be " ++ show numExpCols) $
               numActCols `shouldBe` numExpCols
           mapM_
-            ( \(colNum, actBit, expBit) ->
-              context ("column " ++ show colNum) $
+            ( \(col, actBit, expBit) ->
+              context ("column " ++ show col) $
                 it ("should be " ++ show expBit) $
                   actBit `shouldBe` expBit
             ) $ zip3 [(0 :: Int)..] actRow expRow