diff --git a/src/Lib.hs b/src/Lib.hs
index e543b65..0f4b79b 100644
--- a/src/Lib.hs
+++ b/src/Lib.hs
@@ -1,5 +1,6 @@
 module Lib
   ( flagTile
+  , revealTile
   , printBoard
   , Board(..)
   , Tile(..)
@@ -18,15 +19,15 @@ data Tile
   deriving (Eq, Show)
 
 data TileState
-  = Revealed
+  = Hidden
   | Flagged
-  | Hidden
+  | Revealed
   deriving (Eq, Show)
 
 type Coordinates = (Int, Int)
 
-flagTile :: Board -> Coordinates -> Board
-flagTile (Board board) (x, y) =
+flagTile :: Coordinates -> Board -> Board
+flagTile (x, y) (Board board) =
   case findTile (Board board) (x, y) of
     (Just tile) -> flagHiddenTile tile
     Nothing     -> Board board
@@ -35,6 +36,31 @@ flagTile (Board board) (x, y) =
     flagHiddenTile (Bomb Hidden) = replaceTile (Board board) (x, y) (Bomb Flagged)
     flagHiddenTile _ = Board board
 
+revealTile :: Coordinates -> Board -> Board
+revealTile (x, y) (Board board) =
+  case findTile (Board board) (x, y) of
+    (Just tile) -> revealHiddenTile tile
+    Nothing     -> Board board
+  where
+    revealHiddenTile (Value 0 Hidden) =
+      revealTile (x - 1, y - 1) .
+      revealTile (x, y - 1) .
+      revealTile (x + 1, y - 1) .
+      revealTile (x - 1, y) .
+      revealTile (x + 1, y) . revealTile (x - 1, y + 1) . revealTile (x, y + 1) . revealTile (x + 1, y + 1) $
+      replaceTile (Board board) (x, y) (Value 0 Revealed)
+    revealHiddenTile (Value value Hidden) = replaceTile (Board board) (x, y) (Value value Revealed)
+    revealHiddenTile (Bomb Hidden) = revealAll (Board board)
+    revealHiddenTile _ = Board board
+
+revealAll :: Board -> Board
+revealAll (Board board) = Board $ map revealLine board
+  where
+    revealLine = map revealSingleTile
+    revealSingleTile (Value value Hidden) = Value value Revealed
+    revealSingleTile (Bomb Hidden)        = Bomb Revealed
+    revealSingleTile tile                 = tile
+
 replaceTile :: Board -> Coordinates -> Tile -> Board
 replaceTile (Board board) (x, y) tile =
   let (firstRows, line:lastRows) = splitAt y board
@@ -58,9 +84,9 @@ printBoard :: Board -> String
 printBoard (Board board) = concatMap printLine board
   where
     printLine line = concatMap printTile line ++ "\n"
-    printTile (Bomb Hidden) = "#"
-    printTile (Bomb Revealed) = "B"
-    printTile (Value _ Hidden) = "#"
+    printTile (Bomb Hidden)      = "#"
+    printTile (Bomb Revealed)    = "B"
+    printTile (Value _ Hidden)   = "#"
     printTile (Value x Revealed) = show x
-    printTile (Bomb Flagged) = "F"
-    printTile (Value _ Flagged) = "F"
+    printTile (Bomb Flagged)     = "F"
+    printTile (Value _ Flagged)  = "F"
diff --git a/test/Spec.hs b/test/Spec.hs
index 993938a..cd3fc37 100644
--- a/test/Spec.hs
+++ b/test/Spec.hs
@@ -3,7 +3,7 @@ import           Test.Tasty
 import           Test.Tasty.HUnit
 
 main :: IO ()
-main = defaultMain $ testGroup "Minesweeper tests" [flagTileTest]
+main = defaultMain $ testGroup "Minesweeper tests" [flagTileTest, revealTileTest]
 
 emptyBoard :: Board
 emptyBoard = Board [[]]
@@ -28,22 +28,45 @@ flagTileTest :: TestTree
 flagTileTest =
   testGroup
     "Flag tile"
-    [ testCase "Empty board" $ flagTile emptyBoard (1, 1) @?= emptyBoard
+    [ testCase "Empty board" $ flagTile (1, 1) emptyBoard @?= emptyBoard
     , testCase "Flag bomb tile" $
-      flagTile hiddenBoard (0, 0) @?=
+      flagTile (0, 0) hiddenBoard @?=
       Board
         [ [Bomb Flagged, Value 1 Hidden, Value 0 Hidden]
         , [Value 1 Hidden, Value 1 Hidden, Value 0 Hidden]
         , [Value 0 Hidden, Value 0 Hidden, Value 0 Hidden]
         ]
     , testCase "Flag value tile" $
-      flagTile hiddenBoard (2, 0) @?=
+      flagTile (2, 0) hiddenBoard @?=
       Board
         [ [Bomb Hidden, Value 1 Hidden, Value 0 Flagged]
         , [Value 1 Hidden, Value 1 Hidden, Value 0 Hidden]
         , [Value 0 Hidden, Value 0 Hidden, Value 0 Hidden]
         ]
-    , testCase "Flag revealed bomb tile" $ flagTile revealedBoard (0, 0) @?= revealedBoard
-    , testCase "Flag revealed value tile" $ flagTile revealedBoard (1, 2) @?= revealedBoard
+    , testCase "Flag revealed bomb tile" $ flagTile (0, 0) revealedBoard @?= revealedBoard
+    , testCase "Flag revealed value tile" $ flagTile (1, 2) revealedBoard @?= revealedBoard
     ]
 
+revealTileTest :: TestTree
+revealTileTest =
+  testGroup
+    "Reveal tile"
+    [ testCase "Empty board" $ revealTile (1, 1) emptyBoard @?= emptyBoard
+    , testCase "Reveal bomb tile" $ revealTile (0, 0) hiddenBoard @?= revealedBoard
+    , testCase "Flag 0 value tile" $
+      revealTile (2, 0) hiddenBoard @?=
+      Board
+        [ [Bomb Hidden, Value 1 Revealed, Value 0 Revealed]
+        , [Value 1 Revealed, Value 1 Revealed, Value 0 Revealed]
+        , [Value 0 Revealed, Value 0 Revealed, Value 0 Revealed]
+        ]
+    , testCase "Flag non 0 value tile" $
+      revealTile (1, 0) hiddenBoard @?=
+      Board
+        [ [Bomb Hidden, Value 1 Revealed, Value 0 Hidden]
+        , [Value 1 Hidden, Value 1 Hidden, Value 0 Hidden]
+        , [Value 0 Hidden, Value 0 Hidden, Value 0 Hidden]
+        ]
+    , testCase "Flag revealed bomb tile" $ revealTile (0, 0) revealedBoard @?= revealedBoard
+    , testCase "Flag revealed value tile" $ revealTile (1, 2) revealedBoard @?= revealedBoard
+    ]