Just no good
Normally a space-invader-esque game would be decent and fun to play but challenging even in the beginning. However, this game failed to hold my interest for even the better part of 10 seconds, and the rest of the 30 seconds were busy spent letting the missiles crash into the planet, since it could regenerate its health (arguably at a slow rate) so long as I could defend it. In the end, I just say to make it more difficult, more challenging, so that it might hold interest for a longer period of time, and you very well might have the ground for a decent game.