Great expansion to the previous version of Hellbent. However, there were some glaring issues when it comes to fps. For some reason the frames are bit low but I still manage to play through the game with the issue.
I would also like an option to remove the filter, this may be on me only as It just limited my visibility to see key items and details but It would great to add an option to remove the camera filter.
Another issue I have is the total darkness among some areas. While there are still lights in rooms, there are some areas that are still dark to point you can't see key items or puzzle interactions. Are there plans to add a useable flashlight or maybe a lighter to balance darkness? Since i'm a fan of fallen aces and there was going to be flashlight utility but its only added as a console command, maybe a useable lighter as a light source would be my suggestion, similar to fallen aces you can use for limited time and you have wait for a cooldown. For the flashlight, maybe add it as a secondary light source that behaves like an upgrade to the lighter but requires batteries inorder to use it.
And finally, the puzzles. The puzzles are simple yet still a change in pace to the game which is nice. However, spoiler alert, one of the puzzles such as the valve puzzle is either guess the password or follow the hint because I found the valves, put it in each pipe then I randomly press E on each valve until the toxic gas in the room is clear. I don't know if I missed some kind of hint or the game is telling me to guess which valve to turn first, second, third and last. My suggestion to this guess the password puzzle is maybe paint 1st 2nd 3rd 4th on the wall except remove the numbers so players can maybe figure out and since theres only 4 valves there won't be a second 'th'. If you're confused heres an example:
So you found the valve parts and you put them in each pipe, however when you turn each valve for whatever reason it goes back to where it was. This could be a password type puzzle, you look at a wall that says: 
th, nd, rd, st
Could it mean 4th, 2nd, 3rd, 1st?
You followed the orders and boom the toxic gas is gone.
The second puzzle which required following the sounds of buttons is actually unique. However, it would be nice if there was a hint telling the player to press the computer, like maybe place a small light source pointing directly at the computer. I only discovered that I have to interact the computer through looking at my crosshair changing.
This is a very lengthy review and I'm very sorry if it comes off as harsh or high expectations. This game has potential even for a prototype, I can just sense that this game will takes its place as a grueling horror game like Condemned criminal origins with an edgy comic aesthetic mix with 1993 doom-like elements, much like fallen aces. Butcher's creek being one those grueling horror games that tries to follows Condemned criminal origins, and maybe and just maybe HELLBENT will too.