I love this take on the tower defense genre. I would have liked to put multiple towers on a single planet. Also the types don't seem balanced, I don't get why you would use a slow tower.
Unfortunately the speed of the planets changes with framerate and on my computer it ran at like 1000fps so the planets moved too quick to see! This completely breaks the game. If anyone else has this problem on linux, here's what I use to solve it: https://gitlab.com/torkel104/libstrangle