What needs to be done

At present, my program plays completely bug-free (as far as I can tell). The problems now are the speed, and the number of moves it can look ahead at.

Speed:
The following image is a graph showing time taken against number of moves analysed. For a large amount of moves (generally during the mid-game phase), the maximum time taken is about 24 seconds. This is quite annoying when playing, and it would be nice if this time could be reduced.

Number of moves:
At present, the program looks 3 moves ahead (that is, a computer move, followed by a player move, followed by a computer move). While this works well in most situations, it makes the program rather useless at evading checkmate, in particular, it can't avoid Fool's Mate. I have programmed it to not actually detect check when looking forward (because testing whether every move leads to check would take far too long), instead it evaluates the boards, and if the king has been taken, the board will have a very low score (because the king is given a value much, much higher than any other piece), and it will infer from that, that there was check a move ago. So because of this, it can't look far enough ahead to avoid most checkmates. Silly thing.