this is fun, but i have a lot of notes.
you should not give us a character holding a sword and a shield that cant attack... i realize we pick up a weapon pretty quickly but it's unclear that we didnt already have one. This lacks an intro or tutorial as well and thus is very confusing at first.
there is little to no sound or visual effects for taking damage (it only seems to happen for certain enemies or obstacles but not for most of them) and thus i was down to 1 hp bar from just walking into the dracula dude trying to figure out if he would talk to me or if he was an enemy. maybe think about vibrating the screen and knocking us back 1 space when we take damage to avoid losing the game from just accidentally holding down WAS or D instead of the arrow keys to aim, cus that happened to me like twice before i started just avoiding the combat.
i had no idea whether that was water or lava or an entrance to a new room at the beginning because everything is basically the same color/texture. when introducing damaging terrain the first time you should probably put a signpost there that says "warning! toxic sludge!" or something, and then later add it in as an obstacle once we are familiar with it. a few levels afterwards you hit us with a different type of ground that also has the exact same damage effect, still without warning. you should think about showing the player which types of terrain damage us and which dont. it becomes abundantly clear which parts are safe after a few rounds of "you can only step on the tile that looks slightly different", but before that it could be introduced more smoothly, IMO.
if im not really doing anything besides opening doors and talking to people with the action key, i feel like it'd be a lot easier if we just activated that automatically when we walked up to those people/objects. i also found myself unable to speak to the guy who gives you the first weapon unless i was standing below him, so i assumed that the controls just werent working when i couldnt use the action or attack buttons.
the lever in the dark room doesnt work unless you're next to it, and it looks like it has a face on it, so i spent about a full minute trying to shoot it from below before realizing that it was just an issue with the action button again, but from a different angle.
once i had figured out the control scheme/gotten a weapon, the enemies were all too easy/ they moved back and forth a little bit but i found that i really didnt take any damage at all unless i walked directly into them. they also completely avoided spaces with gems on them, and seemed to even run away from the player most of the time, so given that the combat is so stilted and there doesnt seem to be any stat system or method of gaining xp, i opted to avoid all of them for most of the game.
you need a scheme where both hands can comfortably sit on the keyboard without having to shift positions, or personally i cant have much fun playing this. why not switch the arrow keys to shoot in the direction they point instead of just aiming, and change the action button to spacebar? it would immediately solve the issue of not being able to aim+ move at the same time. i would also have a lot more fun with this if i could hold down the movement keys instead of pressing them over and over v. rapidly.
the music stopped after about 5 mins. im not sure if it's set to loop at all, actually. if so it only looped 2-3 times tops.
i accidentally went backwards through a door and found that they took me to the beginning of each area, not actually to the place where that door was located in the previous area, so after a few attempts to go back to the latest area, i ended up nearly at the beginning of the game with every enemy respawned.... needless to say this was very frustrating. i kept trying and picked up some more gems and potions, which were helpful i guess (i still dont know what the gems do), but then when i hit the room with the 4 bear/cat things, the portal didnt open after i killed them and i was stuck. tbh i am not sure i have the patience to replay this again given that i basically just did the entire game up to this point twice and ran into a 2nd game breaking glitch...
i actually enjoyed this a lot, but this is where i've gotta call it quits. i hope you get some of these issues fixed up (although i know some of the things i brought up are a matter of personal preference). good work!