Tic-Tac-Toe

start state
 +1 (this is a winning state for player X)
+---+
|OOX|
| X |
|OX |
+---+


x's turn

 +1              -1              -1
+---+           +---+           +---+
|OOX|           |OOX|           |OOX|
|XX |           | XX|           | X |
|OX |           |OX |           |OXX|
+---+           +---+           +---+


y's turn

  0      +1      -1      +1      -1       0
+---+   +---+   +---+   +---+   +---+   +---+
|OOX|   |OOX|   |OOX|   |OOX|   |OOX|   |OOX|
|XXO|   |XX |   |OXX|   | XX|   |OX |   | XO|
|OX |   |OXO|   |O  |   |OXO|   |OXX|   |OXX|
+---+   +---+   +---+   +---+   +---+   +---+


x's turn

  0      +1              +1               0
+---+   +---+           +---+           +---+
|OOX|   |OOX|           |OOX|           |OXX|
|XXO|   |XXX|           |XXX|           |XXO|
|OXX|   |OXO|           |OXO|           |OXX|
+---+   +---+           +---+           +---+