There's a lot of potential here for a really good game, and I had fun playing it for a little while. But this needs a lot of work to be a truly good game.
It's nothing fancy, and that's fine. I could stay here for a long time just whacking at enemies and getting more cool looking stuff. It's actually not too bad to find a chest room and wonder, "Oh, is this going to be a cool helmet or a crappy one?" I kept finding normal-looking wooden swords until I found this freakin-sweet Wolverine claw - that was pretty satisfying. I replaced my alright-looking iron helmet for an awesome wizard hat after a while, which I was totally surprised to find!
My issue was mainly the pointlessness of some of the features. For one thing - why have all the prizes in the chests if they do nothing? They felt like an upgrade until I saw they did nothing for my stats! It's just a shame that I explore this place looking for loot, and for what? Why do I need the loot if they don't change a single thing? I replaced the stick with the wooden sword, and my attack didn't go up - are you saying that a stick is equally as effective as a sword?
Now I'm going to clarify - this kind of design is FINE. It works in other games - Little Big Planet is basically comprised of this system. But this is a hack and slash game where I kill monsters, and I want gear that will help me hack and slash. What does the sword do compared to the wolverine claws? Why pick up the new shield if it does nothing for me? I strolled past treasure rooms without hesitation after a certain point because they feel tedious to open for treasure that probably sucks or doesn't fit my tastes.
I don't see the point of safe rooms. They don't restore health, and even if they did it would be pointless because I'm leveling up so much! If the game were more challenging, then you could give it some use as a real 'safe point' - like, "Oh god, I can finally relax!" Give it a real function, like a checkpoint or a healing spot. Right now, it doesn't feel like a safe room, it just feels like a filler room to walk across to get to the next battle room.
Your 'Traps' are not a challenge. I walk into a room, and I step on a firebomb. I keep walking, end of story. What's the point of that? Maybe if you surprised me with something I could avoid, something I could see coming, then there would be real fun. Say one of the trap rooms had falling rocks like the one onion boss guy had. There would be tension to escape the falling rocks, and you can't just run through the room, right? You have to actually dodge the rocks or else you'll take a lot of damage! That's a trap that's fun to encounter, it's a challenge, and you didn't have to force the player to step on something like a cheap mine.
It's fine to have a game where you run up to things and hack and slash them, but it's like you wanted there to be more (the traps! The safe rooms!) but you just couldn't add real content to those areas. But I wanted more, man! Like, what's the excitement in finding 4 chest rooms in quick succession? What's the point in a Safe room that's just in the way of me hacking-and-slashing - in a game about me hacking and slashing? It's just filler! Put something in there that the player will remember, and they will be enthralled with your game.
This game didn't have to be fancy! Even the really simple, easy bosses were nice to fight. They had patterns that I had to learn to exploit, like the bee boss. "Oh, so he goes up to sting me, I'll just go under him and I'll be fine!" That's cool, it's tight. It's good game design to give enemies something that you can exploit. The enemies are a bit repetitive, though. Maybe if the rooms had different enemies inside of them (say, a room with both slimes and squids, mixing it up from the usual combos) then it would be much more interesting!
Overall, this can be a really good game in the future. I'm glad that you're planning to update it, and look forward to seeing what you do! I'm giving this one and a half stars because it doesn't really feel finished. You should totally keep adding to the rooms, the chests, and however else we interact with the game. I had fun fighting the monsters, and I say you should keep on building onto the fighting aspect of the game.
I hope you found this review helpful and constructive, and sorry if it seemed like I was yelling at you (exclamation marks are very fun to use!). Good luck where you may need it, and keep up the work!