Rules for TacTic
TacTic was invented by Terry Godfrey. This Java implementation was created by Garr Godfrey.

The object of the game is to get as many of your pieces in aligned as possible. Align you pieces in a row, column or diagonally. Each sequence only counts as one sequence. You cannot score a run of 4 as 2 runs of 3 and a run of 4.

For each run of 3, score 2 points.
For each run of 4, score 5 points.
For each run of 5, score 10 points.

Why are there squares blocked off?

There are 3 squares blacked out to create an asymmetric playing field. It turns out, with a symmetric playing field, that the playing going first can take the center square, and mirror the moves of his opponent. This will guarantee at least a tie, and will usually result in a win. This is too much of an advantage for the player that goes first, so the symmetry is eliminated.

The computer makes its move determination without any look-ahead. Its logic is almost simple, it sums the number of points it would get from a move and the number of points the opponent would get from the same move, and adds some points for getting 2 in a row (which would be no points) or for a blank at the end of the row (which would create a chance to extend the sequence, for more points). The square with the most points is the square played. The computer used to choose randomly among squares of equal value, but now always chooses the first square.