Hello I''m making a Tetris clone, and I want to implement a versus cpu mode. Does anyone know how can I create the AI for the CPU?

A reasonable idea would be to take the current state of the game, take the new block and create a series of potential new game states with the block in every position under every rotation. Then analyse each of these new world states with a heuristic and pick the best one (for difficulty levels, you can pick the best one for the hardest difficulty, pick randomly between the best two to make it easier, between the best three for an even easier level etc.).
For heuristics you could use several criteria which would become obvious when you play the game yourself.
Examples would be...
...the new game state that has the lowest height of blocks in each column (this could be average height, lowest single colum height or highest single column height).
...the new game state that completes a line
...the new game state that leaves the least number of empty gaps blocked by higher level blocks

To make the AI better you could look at all the potential new game states for the next two blocks with the same heuristic or even the next three or more blocks. To be honest there''s nothing wrong with the AI cheating if it makes for a good game.

Mike

You should add the possibility of AI moving blocks too slowly. Most human players can usually say what place is best (or at least good) for new block, but when the game gets too fast you just don''t have time to move it there.

You could make the decision like MikeD suggested and even evaluate states for few following blocks (using all the possible block combinations, not the ones actually coming). When the speed is slow you could evaluate for example three levels of blocks and when it gets faster you would reduce the number of levels
evaluated.

It is also very likely that the AI will be too good compare to player if you don''t let it make mistakes.

-Ratsia

If you have ever read the Xanth novels by Piers Anthony, you know of the character "Com Puter" If not, here is something. Com Puter is totally logical. A girl tried to teach him Solitare and Freecell. However, she couldn''t do so. It turned out that he had to know how to win in order to play. So, you have to program the victory conditions, so the computer can work with it. However, attempt a skill slightly under yours, or you would tie. (Unless theorhetically, you act in desparation, an emotional feeling. In which the computer would be unable to match your level.)