Thanks! Yeah combining TD with light puzzle/mystery elements maybe wasn't the best idea. :D I thought people would enjoy figuring things out, but I guess not! Also, things are definitely more vague than originally intended (e.g. I wanted the yellow towers, that slow enemies and slightly damage them, to have a simple visual effect). I had hoped to have a little polish time at the end but I didn't. I just updated the game's page with an explicit explanation of it all, for people who are stuck or curious.