Thanks Rewxarx, ill try making it so it gets harder quicker and has a higher density cap. Also i may make it so that the asteroids slowly get faster, and possibly adding a story mode? (like with levels with set things and bosses). Thanks again for the support and advice as i am reasonably new to developing and it is helpful hearing your views. ;)
Lol , i wanted to make a sutable habitat for worms and fish, wondered what virus did, placed a single pixel of virus and then it spreaded and destroyed the whole map. -.-