Currently making my own top-down shooter so decided to give your demo a try and give you some constructive feedback from another game dev in the same position.
Minor things I noticed: I can’t shoot during iframes, maybe this was intended and if so then maybe give the player a slight benefit like a speed boost or knockback because it feels like a timeout. The gun pivoting is off, maybe set the sprite’s pivot to the back of the gun so it feels like it’s being held properly.
Think about camera placement, having the camera lock to the player is fine for now but give them some control or think about how you would place it over the action. For example 'Enter the Gungeon' places the camera between the cursor and the player.
Feedback – give the player more of an idea what is happening in the game. When monsters die maybe give them a bit of knockback and make it satisfying. Add in proper doors/barriers so the player knows they are locked in. The minion spawn maybe needs to be bigger and or make a sound (especially when off screen). I noticed some enemies would come out of nowhere and not sure if this is a bug or a result of this.
Controls are fine, maybe put reload on ‘R’.
Art – maybe not something you’re worried about too much right now but try to keep to a colour palette and style. The exit blends in too well with the floor, maybe I’m dumb but I completely missed it on my first floor.
Now more high-level, if you want to work on this more and finish this game think about a core mechanic. Some design choice or aesthetic or gameplay that makes me, or anyone else want to play your game. Also give me a reason to explore the whole map, good rogue-likes give you a reason to explore and find new things to get upgrades or other pickups. Secret rooms or map interactables are a really easy way to do this.
This might seem like I’m ragging on and maybe some things you’ve already thought about, but I would like to say that the game seems quite polished currently and you’ve clearly got a grip on what you want out of the game. The map generation and seems good and definately something you could build upon with time.