Last updated : July, 2006.

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@F.Pittner

mail@tothello.com

A short guideline of how to play anti reversi

Were you afraid of moving into an x-square? Now you can definitely try this out. One could think that playing a reversed game is too simple. It would be so if the opponent played the normal game mode (gaining the majority in the end). But if the two players play the same reversed strategy it becomes difficult. When I saw my program playing against other human players, I realized that nobody knows how to play a reversed game.

Unfortunately :) I will not be able to give you clear guidance regarding playing reversed games, however since I have been observing my program playing for a long time, I can provide you with some advice:

• Mobility is the most important. This is difficult to formulate, but try to occupy the interior territory and let the opponent occupy the borders. In the next picture white has a nice inner position and feels lucky about it .

There are nice descriptions available on the web about mobility and how to minimize your discs from the frontier. Why is mobility so important? Because you can force your opponent to move into those squares which are disadvantageous to them. If you manage to build up a configuration like this:



 

then this corner will never be occupied by you. This is the simplest example of forced mobility in case of the anti games. Unfortunately this doesn’t guarantee that the corner will really be occupied by your opponent, but it is at least a strong position/threat.



 

In the next game position I was happy to have occupied A2 and created a closed corner playing black, but in two moves the computer will force me to occupy H1 (H2, C6, H3).

 

This is a very good example of the great difference between the endgame results of normal and reversed games: despite this being a very disadvantageous situation, this game ends with a difference of only about 24 pieces and not 64 (of course white wins).

 

My program calculates six types of mobility. I observed that it struggles to gain as much mobility as possible (even if, for instance, it needs to make a pass in order to accomplish this goal).

• Don’t move into corners too early. I’m sure you understand this.

 

• Squares’ importance: one can think that in the reversed reversi B2, B7, G2, G7, and the squares adjacent to the corners are the most important squares. During its learning Tothello calculated the board squares’ order of importance. It’s a miracle, but the squares mentioned before are at the end of the list. The different squares’ importance is as follows (in decreasing order of importance ):

8x8 board (reversed mode)

C4, C5, D3, D6, E3, E6, F4, F5, C3, C6, F3, F6, B4, B5, D2, D7, E2, E7, G4, G5, B3, B6, C2, C7, F2, F7, G3, G6, A4, A5, D1, D8, E1, E8, H4, H5, A3, A6, C1, C8, F1, F8, H3, H6, A2, A7, B1, B8, G1, G8, H2, H7, B2, B7, G2, G7, A1, A8, H1, H8, D4, D5, E4, E5.

Obviously, the last four squares are of course there to complete the list. In a normal starting configuration they are already occupied.

7x7 board (reversed mode)

C4, D3, D5, E4, C3, C5, E3, E5, B4, D2, D6, F4, B3, B5, C2, C6, E2, E6, F3, F5, A4, D1, D7, G4, A2, A6, B1, B7, F1, F7, G2, G6, A3, A5, C1, C7, E1, E7, G3, G5, B2, B6, F2, F6, A1, A7, G1, G7, D4

 

on 6x6 board (reversed mode)

B3, B4, C2, C5, D2, D5, E3, E4, B2, B5, E2, E5, A3, A4, C1, C6, D1, D6, F3, F4, A2, A5, B1, B6, E1, E6, F2, F5, A1, A6, F1, F6, C3, C4, D3, D4

 

• Don’t flip too many pieces. Try to flip minimal number of pieces, your intention is to have the least of them in the end, if you flip too many, you will have more and more.
• Practice as much as you can. See what strategy a “more experienced” player follows.
• Risky moves. And something interesting at the end: Many times I have observed my program making the following - apparently dangerous – move like C1 in the next picture:

I think it is a really risky move, but you gain mobility by going for it. If you can handle the situation afterwards, I would recommend making such moves.

Finally: just to convince yourself about the “real” importance of corners and corner moves in reversed othello , just try to play and win against Tothello in a reversed game with the following opening/starting position (Tothello plays white):

Enjoy!