It was bothering me that you had written GORILLAS.BAS as I remembered it as GORILLA.BAS. I hadn't seen it in 27 years, at least, so I wasn't confident. Anyway today I had a look, and we're both right.

The game was called GORILLAS, but was in a source file GORILLA.BAS

Published in 1991, 32 years ago. Dang. It was pretty new source when I read it. At the time, I figured it was old.