I honestly don't understand why people complain about these being BOTD so much? take 20 minutes and play until you get both badges, then you never have to worry about it again. sure it's repetitive and a little boring but honestly once you get the badges you never have to play it again.
I appreciate how the invaders will stop and wait for a skeleton to catch up with them once the skeleton kills whoever they were fighting with. Really good sports.
Tips for the medium badge: For your first couple bullets, only shoot the fast ships. After that, don't shoot unless you have 'fire for free' up, or there are absolutely no other bullets on the screen.