Simple game that fulfills its purpose.
Suggestions: scale enemy health as the match progresses to make it more challenging. After collecting a few damage upgrades, all enemies die in a single hit. The opposite also happens, at the beginning of the match, it’s not worth picking any upgrade other than damage. Ideally, the player shouldn’t be punished for not choosing damage early on, and other builds (like attack speed with low damage) should be viable.
The animation for when the player takes damage is the same as when they pick up XP (screen shake). Sometimes, when enemies are nearby, it gets confusing 'did I gain XP or did I get hit?'
Another suggestion is to add some incentive for the player to move around the map. It’s completely empty and, in practice, there’s no advantage to walking around. Adding a treasure or something similar that grants extra XP or a free power-up or health could encourage exploration. I also suggest slightly reducing enemy collision. In survivor-like games, the feeling of 'barely making it through' is very satisfying.
Overall, good game. I wish you success!