Strategy
As one rapidly discovers in playing Critical Mass, play is dominated by several factors:
- Position is unstable: This is to say that an apparently weak player can (and frequently does) reverse the tables, by detonating a chain reaction that takes over most of the board.
- The edges and corners are the most important cells to take, as with games such as Reversi (Othello).
- If you only control a few cells, you will be forced to place more and more pieces in those cells. When you explode them, your opponent will normally set off a chain reaction that deprives you of the original cell.
- The results of a move become progressively harder for humans to predict as the game continues.
- The computer has some difficulty determining good moves early in the game.
- As a result, humans should concentrate on dominating the game from the beginning.
In addition, some observations can be made about the computer players:
- All computer players choose randomly between all equally-good moves available to them.
- The computer players perform simple min-max searches, to the following depths:
- Smart: 1 level
- A.I.: 2 levels
- Bill Kocay: 4 levels
With a branching factor that often approaches 30, this is ample to keep even a quad-processor machine busy.
- Computer evaluation of board positions is weighted to emphasize edges and corners.
- Against the smart level, an effective trap is to leave a corner square open, with two of your pieces in an adjacent square. When the computer takes the corner square (as it almost always will), explode the cell next door, and take the corner. This is not effective against A.I. (it can see that you will do this, and avoids it).
- The computer is rather less effective when playing with wrap-around turned on. Or even on the torus.
If you come across consistently effective strategies, please let me know.