You could spice up the main menu by adding a moving background (a time-lapse day/night cycle of the starting map, for example). I noticed some bugs during my playtime: if you close the pause menu while the controls submenu is open, the game resumes but the control screen doesn't close; the settings also reset to default upon death. Some advice for possible changes to make the experience more polished and fun: if you want to use in-world UI, a better solution would be to simply use health bars instead of the current cross. This makes the game look cleaner and less cluttered. You should also consider visually depleting this bar to make it more readable how much HP the enemy has left. You could also make the enemies spawn one after another to throw the player off.
Ideas for future additions:
- Make the levels more interesting by introducing more obstacles, so it gets harder for the player to just run in cycles.
- Slowly introduce different enemy types into the game. Make enemies that move at different speeds to make the horde less predictable, include some size variations, some enemies that can fly, some that use ranged attacks, some that try to cut off the player's path, and some that are even stationary.
- Another way to make the levels stand out more from each other would be to place some traps in them (spike traps, mines, turrets, etc.).
- After a stage is completed, you could reward the player with a choice of 3 random chests and show a visual representation of the item they got.
- You should also implement a way of looking at the current stats or items.
- After the stage, spawn a door on 3 (or 4) walls of the level and let the player choose one to go to the next level. Make the transition seamless instead of just teleporting the player there.
Additionally, you would need to introduce a more complex combat system by either adding some kind of weapon system or building a solid system that can be fun on its own (which is a lot harder to do).
Overall, I think this project needs a lot of work to become really fun, but if you decide to stick with it, it could turn out great eventually.