Do you think all astronauts are smart? It is definitely not about these guys, because they are sure visiting a black hole is quite a funny idea. Your mission is to save them!
Spin circle of portals, catch astronauts and save them all from becoming ghosts in depth of the black hole. Though, even worse is to catch them with portals of inappropriate color - energy fields overload will destroy portals and the last hope of the astronauts.
Deal with special events, be happy with buffs you pick up from yellow stars, but try not to lose because of debuffs you get in the same way, use and upgrade skills to move even more forward!
All in all do your best in controlling portals circle as long as you can and have fun!