A lot of the inspiration of this program came from the book "Computer Chess" by David E. Welsh. Except for the lack of an opening book, the program uses a search technique similar to those used by chess programs.

Update: Now I have a new version of the program for the very fast PPC Macintoshs available these days. With older Macintoshs, the higher skill levels were absolutely unusable, do to the time it took the computer to calculate a move. When running the old program, current generation machines can calculate a move quite quickly even at the highest level . For the new version, I have increased the number of skill levels by 5. Everything else is the same. Let me know if you want a version that goes even deeper (and slower).

One trick you can use to see what the computer is thinking about is to flip between the Cinco window and another window while it is calculating the next move.  When the Cinco screen refreshes, it will show the move it is currently looking at.

I have heard of issues with folks having trouble with downloading and extracting the program. If you have trouble, try expanding with an application called Zipit.