After making Extended BASIC suggestions to Opry99er and Primordial Ooze, and skimming through the handbook last night, I've decided that my XB skills aren't as rusty as I'd originally thought, and I know enough to at least start on a new XB game. I don't want to go too much into it yet, since real life, unfortunately, has a lot of demands on me right now, and I may not finish it anytime soon.
I will say, however, that it won't have a conventional scoring system. Scoring will be simply a way for the game to decide when you're ready to engage in a "boss battle." The game will require TI Extended BASIC, but will otherwise run on an unexpanded TI (i.e., it doesn't require E/A, 32k expansion, etc.). I'm toying with the idea of using speech, but it will depend on how large the program ends up being, and whether I feel it actually adds anything to the gameplay. If I have room for a title screen, I may be asking Owen for help with the title screen music.
Oh, and it's loosely based on a movie that came out around the time of the TI-99/4A*. Feel free to engage in speculation. ^_~
*disclaimer: not "at the time the TI came out," but "around the time of the TI's original lifespan."