3D Noughts and Crosses Debugged!

Here it is game in progress. The bug that took QL Heaven 3 weeks to track down was in the location in the code that it was thought to be. It escaped examination of the code while running the program. It escaped notice while cross checking a printout of the listing against the original listing in the magazine. What identified it was manually checking the calculations that these few lines did. Then the penny dropped. Of the three calculations two called the invert function. One did not, but in the listing QL Heaven had typed in all 3 did.  Hence the unexpected outputs of the program but not an obvious crash. It goes to show that you see what you expect to see and that's is the sole reason why it took so long to track this particular bug down. The program seems to play a reasonably mean game. But it is early days and as its strategies become known it may eventually prove to become a pushover. This thought makes QL Heaven think of some AI listing that had been published in QL World at some time. Could they be incorporated to give the program an opportunity to learn the style of its opponent as well?

The immediate plans for the program are to refurbish it with a movable window, perhaps re scalable, GD2 driver colours some icons instead of the filled in squares.
We will see what can be done.