diff --git a/play_ttt.py b/play_ttt.py
index ef5530a..afce7cb 100644
--- a/play_ttt.py
+++ b/play_ttt.py
@@ -7,9 +7,12 @@ player1 = TTTHumanPlayer("Player 2")
 game = TTTGame()
 view = TTTView(player0, player1)
 
+# creates blank board
 state = game.get_initial_state()
 view.greet()
+# gets passed blank board at start
 while not game.is_over(state):
+    # take an action and update board
     action = view.get_action(state)
     state = game.get_next_state(state, action)
 view.conclude(state)
diff --git a/ttt/game.py b/ttt/game.py
index 2f0e302..26d6f35 100644
--- a/ttt/game.py
+++ b/ttt/game.py
@@ -26,6 +26,7 @@ class TTTGame:
 
     def is_over(self, state):
         "Checks whether the game is over."
+                # FALSE because blank           FALSE because no markers        FALSE because no markers
         return self.board_is_full(state) or self.check_winner(state, 'X') or self.check_winner(state, 'O')
 
     def get_reward(self, state):
@@ -58,4 +59,17 @@ class TTTGame:
 
     def check_winner(self, state, symbol):
         "Checks whether the player with `symbol` has won the game."
+        currentState = state["board"]
+        # possible tic tac toes: 012 345 678 036 147 258 048 246
+        for i in range(0,7,3):
+            if currentState[i] == symbol and currentState[i+1] == symbol and currentState[i+2] == symbol:
+                return True
+        for i in range(3):
+            if currentState[i] == symbol and currentState[i+3] == symbol and currentState[i+6] == symbol:
+                return True
+        if currentState[0] == symbol and currentState[4] == symbol and currentState[8] == symbol:
+            return True
+        if currentState[2] == symbol and currentState[4] == symbol and currentState[6] == symbol:
+            return True
+        
         return False