iFreeware

Play Square Four online or with AI.
Square Four is a game takes place on an 8x8 board, original concept by Scott Kim.
The rules are simple. Two players take turns placing pieces on board, these pieces are immobile once placed. The object of the game is to make squares with these pieces. The larger the square, the more points it's worth.
Squares may be tipped at any angle, in fact the diagonal squares earn big points. The way to determine the points of a square is to count the square of (maxX-minX+1), where maxX is the horizontal position of rightmost piece, and minX is the horizontal position of leftmost piece.
You win when you get over 150 points with at least a 15 point lead over your opponent.