Nine feckin' years, and I think I might, finally, have it.

I downloaded a torrent of TI994A games a while ago but never bothered looking through them. While searching my hard drive for a copy of Cave Story just now, I happened to notice there was a game called "Old Dark Caves 2" that I didn't remember seeing in any of my browsing before.

So I Googled <"dark caves" ti994a>, which brought me to http://tigameshelf.net/xb.htm – AND THERE IT WAS.


Void, by Gregory Kean
This is a somewhat surreal game with a science fiction feel where you are trying to move from one level to another by jumping over moving obstacles that will kill you on contact and activating the doorway to the next level. Requires precise hand eye coordination and cool nerves. Very original presentation and addictive albeit difficult gameplay.
An extended BASIC game, "recently rediscovered" as of September 2009, according to http://www.retroclouds.de/#post8 . (That would explain why no such game is, in fact, in that archive I downloaded.)

The mystery, it seems, is solved at last! Now I just have to figure out how to get it going, and then be immensely disappointed.