Found another old Game Maker (5 or 6), almost 20 years ago, tentatively titled "Berzerk X". The robot sprites were made in Doga CGA, a Japanese 3D modelling program that mostly consisted of prefab spaceship parts. Background/wall sprites were from a site called molotov.ru that now seems to be something else.
Now that I'm picking up gamedev again I kind of want to finish some of these. Or at least put the code up somewhere for people to laugh at.