I just came across a video on YouTube about the original Halloween Harry:
Is this actually related to the Apogee game?
It's made by the same guy, John Passfield.
Ooh, that's cool. Welp, now I want to boot up my retro rig and play Alien Carnage again.
Primitive but at least no need to keep recharging fuel or weapons, which is annoying with HH (Alient Carnage.)