It has two difficulties: Story & Professional.
I've only played/beaten Story. I still feel like it's difficult.

The game is good.
Basic loop of explore, find a puzzle, find a key or solution, go solve it, and repeat.
Combat is done as first person and you're stuck in place. At some points you'll need to whip around and use all 360 degrees, but generally it's just 1 direction or 120 degrees. Combat also has zones on the normal enemies to give you good feed back (leg shots can turn them into crawlers, head shots do extra, 'glowing points' are crits, and there is a parry system).

The exploration phase feels great on controller with how everything interacts, but works well on Keyboard n Mouse.
The shooting with the combat phase seemed kinda standard for a controller (I didn't care for it), but felt good to go on keyboard and mouse

Inventory management is gentler than RE, but harder than SH. Each character has 'so many slots' for healing, ammo can be refilled 'up to a base amount' if you head back to your refill point. Ammo feels limited and was in need until a tipping point near the last 1/3rd.

The story is generally B with just enough juice to really enjoy.
The puzzles were generally understandable (only had a problem with 1 of the 5 or 6 in the game).
I felt like there were about the same 5-6 'boss level encounters' that push you to your limits and maybe beyond, but you later are better able to deal with them (Not just item improvements, you better understand the game).

Overall it is a Nice little slice of horror.

It says I have 11.5 hours at this time, but I left the game up for about 3 hours while I did other things as you seem to have some level of respawns if you save, quit, and return (this could just be story related 'next spawns' coming in).

Feels a little short for 20, but 15 is an easy recommendation. 10 is a great deal.
I will eventually go back to try out hard mode and get the last few achievements (all of them are reasonable).

Conclusion : for the price obtain in sold (around 4€) , the game can be recommended even though it didn't seems a "finish / polish" game. At the real price, i wouldn't recommand it unless you are a real fan of "rogue like" , "try and retry game".

It is honnestly difficult to give a proper assement of the game
=> The game seems to want to be "resident evil" clone and did a decent job for the ambiance.
=> It has a psycological approach which try to mess with you (with limited spoil).
=> It work like a rogue like with a story behind.

However you don't know the limit betwenn the bug or choice of gamedesign. For exemple :
=> With limited spoil : the first ennemy you will meet will take 2 bullets if you shoot the head. So you will learn a first basic that should help you. But next ennemy (and the two following) will take two bullets for the first phase then 5-7 depending if you control your gun.
(*) They would be all zombies but as the first one is extremely easy other will rush and force you to shoot fast
(*) You can decide to defend yourself but after two attempt of break out you will be bitten.
(*) For the more resistent ennemy, you will most likely try to empty your gun fast as when they will pass in phase 2, they will rush at you. However, take in account that the reload animation is extremely slow leaving you time to get caught.

=> Early in the game : you will meet two zombies in the same zone (one in a room you need to go and the other in the corridor). Fight them will be useless as explain before, so you will most likely attract them in an empty room close both and run to get to the other room where you need to get an item. It will works so well that they will stop following.

=> None of the special force has a flaslight. Some parts can be tricky as they are dark and if you don't know that an ennemy will wait for you, you can be trick easily.

=> In an underground part : you will have lever to trigger (spoil limited). You will meet a new type of ennemy which will be sleeping, wake up in some case and will have a forward lunge attack that you can dodge with timing. However
a) If you pass next to the same cage, at different range, .... It seems to randomly wake them up. I try to get far from line of sight, not run ... but sometimes it works, sometimes not.
b) At a certain point, you will have a level in a really small corridor where you will have at least one of the ennemy following you (up to two if you accidently trigger an aggro). You will be abble to hide behind the level to avoid the lunge and ennemy won't make the turn to rush you. You will be able to get out, however
(*) Even if you wait the "stun" of the lunge attack, it seems to still trigger a fight.
(*) The game will make you start with a new weapon you will collect earlier : it won't consumme ammo but you won't have any defense so you will take dammage no matter what. You can switch though to your pistol.
(*) As you finish the first fight, the second one will automatically trigger.

=> At some point the game will block you to go backward. It won't be tell to you intially so you need to look around as much as possible.