Fun spin on the tower defense! The game feels overall very polished and kudos for managing to make a fully fledged game with all assets "home grown" ^_^
Have you considered having gloops drop ploop coins and ploops drop gloop coins? Might be interesting to have it be codependent. Maybe you already tried it and it wasn't as fun as it sounds?
Outside of the main game the menu is very pretty and fun looking. I personally love the included concept art on the credits page.