Pretty fun game! I played through the demo and I think you are a bit too generous with lives. I had around 18 left and I wasn't even being very careful. It was also a bit unclear to me when the power-ups expire exactly and the collision for going around corners was a bit strict. Not sure if you want to emulate that from DOS games too or if you want to make it smoother, I can see a case for both. I also couldn't figure out how to use grenades, I'm guessing frags is your number of grenades but none of the hotkeys worked for me. I also liked the puzzles and having puzzles during combat encounters but I don't like how the levers constantly switch when you're just shooting enemies, maybe they should have a short delay or something.