I put in the collision detection. It works just fine. I added some support for 2 more banks. If you press 1 on the title screen it goes to bank 1 and pressing 0 will send it to bank 0. But the game goes crazy if you do because those banks aren't in the game yet. When I make banks 0 and 1 and insert them into the game it should work then. I will change it from pressing 1 to pressing the multiply sign (because it looks like an x) and 0 can stay because it looks like an O.
Since I put in the collision detection, I had to make it disregard an O getting hit by his own missile. This would happen if he was on the extreme left or right of the screen and if he was up high when he shot it on the extreme side and then came in lower again on the same side, he'd get hit by his own missile and the game would end. So I decided to disregard a hit from O's missile if the O was on the extreme left or right of the screen. And, of course, make it so the X can't go there.
I also made it so if an X hits an O, an explosion sound happens, a point would be added, and a new O comes on screen. I also had a bit of trouble making the score disappear when the game ends and you then go into the tic-tac-toe game. The score would still be there. So I had to make some adjustments to that code, and then more to fit in making it go to banks 0 and 1. Fortunately, it all fits in there in (very tightly).
What's next to do is work some more on the "main" game to make it better. But I will take a break for Halloween/my birthday and resume work on the third. Really don't want to get angry on my birthday.
I had been wondering why my room had been so hot. I discovered the floor vent was open. So I closed it, but it didn't seem to help much. I guess it doesn't take very much to get me hot.