Although that might seem an impressive number of moves and counter-moves, in reality Tic-Tac-Toe optimal moves can be resumed in simple sentences and logical thinking. ..
From Wikipedia:
"A player can play a perfect game of Tic-tac-toe (to win or, at best, draw) if they choose the first available move from the following list, each turn, as used in Newell and Simon's 1972 tic-tac-toe program.[8]
Win: If the player has two in a row, they can place a third to get three in a row.
Block: If the opponent has two in a row, the player must play the third themself to block the opponent.
Fork: Create an opportunity where the player has two threats to win (two non-blocked lines of 2).
Blocking an opponent's fork:
Option 1: The player should create two in a row to force the opponent into defending, as long as it doesn't result in them creating a fork. For example, if "X" has a corner, "O" has the center, and "X" has the opposite corner as well, "O" must not play a corner in order to win. (Playing a corner in this scenario creates a fork for "X" to win.)
Option 2: If there is a configuration where the opponent can fork, the player should block that fork.
Center: A player marks the center. (If it is the first move of the game, playing on a corner gives "O" more opportunities to make a mistake and may therefore be the better choice; however, it makes no difference between perfect players.)
Opposite corner: If the opponent is in the corner, the player plays the opposite corner.
Empty corner: The player plays in a corner square.
Empty side: The player plays in a middle square on any of the 4 sides.
AND THEN
To guarantee a draw for O, however:
If X does not play center opening move (playing a corner is the best opening move), take center, and then a side middle. This will stop any forks from happening. If O plays a corner, a perfect X player has already played the corner opposite their first and proceeds to play a 3rd corner, stopping O's 3-in-a-row and making their own fork.
If X plays center opening move, O should pay attention and not allow a fork. X should play a corner first.
If O takes center (best move for them), X should take the corner opposite the original, and proceed as detailed above.
If O plays a corner or side-middle first, X is guaranteed to win:
If corner, X simply takes any of the other 2 corners, and then the last, a fork.
If O plays a side-middle, X takes the only corner that O's blocking won't make 2 in a row. O will block, but the best of the other two will be seen by X, and O is forked. The only way that X must lose is if O plays middle and then a side-middle"
"
That might seem overly complicated, given the simple nature of tic tac toe, and in fact, it really is. If you have good logical reasoning and know the basic rules of tic tac toe, you already make the optimal choices after every opponent move, unless you make a mistake, that is. It is rather simple to devise from simple trial and error these simple rules, and while you won't have them as such inside your head, your brain will automatically make these decisions for you. There are only 9 positions on the board. There are 7 winning configurations. Line 1, 2 and 3, Column 1, 2 or 3, and diagonals \ and /. You simply have to prevent that configuration from happening, which isn't hard.
The number of possible plays and counter plays is a very big number, yes, but the nature of the game makes it so simple that i, myself, do not consider that you can possibly "minmax" in a game of tic-tac-toe. You either deliberately lose, lose because you didn't pay attention to the whole board, or you draw, or your opponent deliberately loses, or loses because he didn't pay attention. That's it...
Since the comparison is bound to be made, theoretically, it's the same thing with Chess, but because the number of pieces is much larger, the fact the pieces have many different rules for movement, and that there are several other rules for draws, promoting pawns etc., and because the board is so much bigger, you can't do with chess what you can do with Tic Tac Toe, which is to write a guide of rules that if you follow, you will win every game. With Checkers, it's the same thing, albeit Checkers is a lot less complicated than Chess, there are still too many possible positions for a HUMAN to be aware of at the same time. The
Chinook program has, as of July 17, 2007, become unbeatable at checkers, because it has in it's database every possible move, every possible counter-move, every end-game, and thus, has in it's database the entirety of the possible games of Checkers than can possibly exist, and thus the best a player can do, no matter how good they are at Checkers, is a draw against the computer... With Chess the are so many possible games(Essentially all the possible moves and counter-moves and end-games )there hasn't been a computer that was able to calculate the entirety of it's game tree complexity of 10^123 possible games. That's more the number of atoms that was calculated to exist in the universe. Way more in fact...
Which is why humans
can still win at chess against computers, albeit it is getting increasingly difficult for a human to do so, as computers calculate more and more possible games of chess, and the programs get increasingly sophisticated at predicting future moves(Something the checkers program doesn't even have to do, since it already has access to a database of all the possible games of checkers, so it always knows what the optimal move is, regardless of the state of the board).
