I played the game for a good 21 minutes, it's pretty addicting! I think the main gameplay loop is quite solid but there could be more like poweups/items that give players more control other than just walking around. I thought the difficulty was pretty good as I was challenged but not overwhelmed with enemies, the boss was a surprise because I had no idea there'd be one.
I found a few bugs. Mainly the fullscreen toggle doesn't work so I was running the game windowed the whole time. Once I pressed to maximize I noticed that therre were black borders around the game screen. I know you're using Godot like me so do look into the window strech/aspect modes in the project settings. Also the music slider didn't seem to change the volume of the music in the game.
Presentation wise I think the game is simple but not in a bad way. Something I'd do is make the slimes have some kinda appear animation so they don't just pop in, could be something as simple as their scale quickly animating once they spawn. If the blue tiles are meant to be water you could look into doing some water shader, there's a lot of cool stuff on godotshaders.com. Also your itch cover is just a screenshot of the main menu but it'd make more sense (and be more appealing) if it was just the background art from the main menu. I was a bit dissapointed at the AI art though, I'd much rather the cover be something with the same artstyle as the main game (I assume those were made by you and not AI).
Overall I enjoyed the game and I think if you add more content it could be even more addicting than it is already!