Nice concept, I love the music in worm mode, pretty difficult, and that's about all there is to say for me. I liked it, it was sweet and simple.
Only thing I'd recommend for future games, and that is a bit of a personal issue not a game design issue, is to avoid using Z/X controls if you can expect the game to be played by an international audience, because keyboard layouts are not all the same, and German keyboards have z and y swapped to English ones so I always have to try out how it was implemented and if I actually have to press Z or Y and it's rarely in the comfortable spot next to X -v- I've encountered this issue in so many games already, just a personal gripe...