This is really addicting. I am surprised you made it in Scratch, that's pretty cool! I love that the art seems to be custom made for this entry (or if it's not, it fits really well at least), and the music is perfect as well. I could absolutely see this being a full game, and personally I really appreciate that you combines survivors-like waves and upgrades with turn-based puzzle mechanics. Love me a good puzzle game. I hope you'll turn it into a full project!