The game is a good one, mostly because it is pretty unique. It was hard to get used to, but worked out eventually. I think the music's pretty sweet too. I liked how you could control the order the enemies were defeated. It can be too much to have numerous layers put on at one time. While not that fancy, it still worked fine.
I think the title is derived from "radius". I never was good at understanding geometry. It could have used more detail. I guess it is kind of hard to suggest detail in a game like this. It is worth checking out.