I like the concept of being the enemy space station essentially. I also really liked the look of the planet and the enemy flagship, it really helped to sell the experience too.
The aim was a little bit weird, it was hard to tell if I was hitting some things and it felt like enemies reached a range at which I couldn't hit them anymore a lot faster than I could help. I think it would help to slow down the spawn rate a little bit at the start just to players a little more time to familiarize themselves with the aiming.