Let me start by saying that this entry took me a bit longer to review... because I couldn't stop playing it! :D
It's easily one of the most impressive and better entries of the jam. Everything about it is near perfection! The simple yet complex system implemented here is incredibly fun and challenging, and the upgrading system is a neat addition. The tutorial provided is simple and effective, allowing me to easily grasp the mechanics compared to just guessing and finding out on my own haha. (though I wish it had something to make it easier to learn but that'll be for later)
While I'm not the biggest fan of AI artwork, it works well within the context of this game. Considering the time crunch and the direction you took, it's completely understandable, and overall, the visual experience is quite nice!
If I had to nitpick, I would suggest having the tutorial as an interactive button rather than a splash image. This would allow players to learn faster and refer back to it if needed. Additionally, introducing some extra variety, such as range enemies or new types, could add more diversity to the gameplay. However, these suggestions are minor because, honestly, for a game developed in just three days, this entry is incredibly impressive!
Regarding the theme, I understand what you mean. It's a bit of a stretch from 'echos,' and it doesn't fit the theme too well in my opinion. Nevertheless, this doesn't detract from the fact that it's a great game. It showcases impressive skills and delivers an enjoyable experience.
Overall, despite the minor nitpicks and the theme aspect, I thoroughly enjoyed playing this game. I highly encourage you to continue working on it because there is so much potential here. Best of luck and wishes to you! Great job!"