The mechanics are solid and the game plays well, I do have a few bits of feedback though.
- Visibility is an issue. You can't see too far ahead, so implementing something that moves the camera to look ahead in the direction of your cursor would be great.
- Enemies can spawn very close to you. It's especially a problem with the "fire flies" that can spawn nearby and immediately shoot a fast projectile. You can lose hp in unpredictable ways because of this.
- Sound effects were a bit lacking. They were being played when they should be, but they were quiet and barely provided feedback for your actions. In particular, I'm referring to the sound that plays when an arrow hits an enemy. It's important because your arrows can hit things that aren't in view and the only thing that can tell you when you landed a hit is the sound.
- The theme hasn't really been implemented here. I understand that the dungeon is endless, but the Ouroboros is more of a symbol for a cycle or a loop.. Each time you complete a cycle, you should end up right back where you started. But here I don't see that cycle or loop, just an endless line of enemy waves. I chose to at least give you something for the theme rating because in the end it is about your interpretation and not a constraint.