Hi,
I made OXO in axe. For those who don't know the game, it's basically tic-tac-toe, but on a larger board, you need to make 'OXO' instead of a row of the same symbols, and making this combination increases your score instead of giving you an instant win.
It's a lot of fun to play with friends (using single-calc multiplayer), but it also includes an AI which should give you a good challenge.
Screenshot:
controls: you can move the cursor with the arrow keys, [2ND] selects an option in the menu or places an O symbol in game, [ALPHA] places an X in game, [ENTER] confirms the settings in the menu, [S] ([LN]) saves the game and exits (saved games are automatically loaded and deleted at startup) and [CLEAR] ends the game.
Have fun!
EDIT: a 15MHz calc is reccomended (AI calculations are quite slow), but it'll also work at 6MHz.
Click here to download Oxo.