This is pretty solid. It has all the pieces of a tower defense game so if you continued to build upon it then it could become something really cool. The overpower bar is already a pretty neat mechanic. I liked the art, the style was minimalist but still had heart and appeal. I can't think of a bug or super specific downside. I would continue to polish it and make it feel better to play with some feedback and juice. If you end up trying my game: Press "Y" to restart the level, "2" to skip levels. (seeing a lot of comments from people saying I need a restart button, I just didn't make it clear.) Good job!