Outstanding game! Amazing visual aesthetics, balanced as it should be, not too much, not too less. The core loop is simple and easy to follow. The music is energetic and perfect for hyping up a simple gameplay.
I like how we can see where and when will the enemy spawn so it don't caught the player off guard from sudden spawn. Also that upgrade on death is nice decision so the flow don't go stale easily, only grow stronger when necessary.
Overall, this is a masterpiece. Carefully thought out design. I don't see any flaw worth mentioning except for it is short which is undestandable because it's just for game jam. The game is polished well and has potential to be a full game.