Two theoretical possibilities for the 4-armored-on-glass.
1. You have to fire once. Grab that guy, throw him into the next, grab him, next, grab him, next. This may be possible, but the glass is finicky and the timing is tight.2
2. You have to fire twice. Shot and grab the first guy, throw him such that the glass breaks under another guy. Do that again with the third and fourth. This is less finicky, but still hard. I didn't manage to do it before I accidentally pushed esc and closed the game. It definitely looked possible, though.
All but one level can be cleared without using the gun at all.
Someone claimed it was every level, but I don't see how you can do the four armored guys on glass without the gun. I might go back and see if I can do it with only one bullet.
Edit: Might be possible with one bullet. Extremely hard.
Looks possible with two bullets. Very hard.
How could you possibly clear the 4 armored guys on glass without using the gun?
You can't kick, because you can't kick when you're seen. You also can't go invisible for the same reason.
And you can't grab them because they're armored.
If there's any way to do it at all, I expect it to be exploit, but as of right now, I don't see any way to do it.
You were right about every other level, though. Thanks for the challenge.
Edit: One bullet on that level may be possible, but extremely hard.
Okay, can I ask why you don't update those versions for which you don't have an error report?
Also, would it be possible to get a Steam key? I purchased the game here (Nov 4, 2019, and I can show you the e-mail), but I find Steam more convenient for consolidating my game purchases.
That being said, I don't want to make a big deal out of it. If it's impractical or inconvenient, I'll keep using it from my Itch.io account.
