Some random feedback
- First time I spawned I got stuck inside of a bat and couldn't move or kill it. The bat wasn't attacking me either.
- I like the perspective but the combination of the perspective and how small things are sometimes fucks with my head and its hard to judge if I am lined up with an enemy/chest or not.
- Camera movement when changing direction is too jarring. I suggest making it smoother.
- No performance issues at all.
- I really enjoy the camera spinning around when you die.
- You probably already thought of this in the long term but having torches as an additional light source on the walls would look dope with your lighting engine. Maybe a small camp of enemies with a bonfire etc.
- The combat feels nice. I can imagine it being really satisfying with some proper sounds and weapons. I don't really see the use of the lock on mechanic outside of bosses for example.
- Make the stamina bar thicker.
- The controls are bit unintuitive. Definately make them rebindable. Using items during during combat is a bit weird with the current keyboard layout as is the lock on. Also give the player an optinon to go fullscreen ingame instead of alt+enter.
- Your UI elements feel to spaced apart.
I suggest putting the attack and defend boxes at the top right below the item use boxes at the bottom left to clean it up a bit. Also you should see if making the coin and kill counters smaller and putting them below the health and stamina makes the UI more compact. 
Pic related to give you an idea of what I mean.
The blue space can be for buffs or mana if you want to use a magic system. Also shows the bat bug.
- The general look you are going for is pretty cool. I would gladly put in several hours if you juiced it up with items, shops, secrets and stuff like that.