To avoid our world getting swallowed by huge, deep and cruel black holes, you need to keep our world in the space that we are already living at the moment. To do that, you just need to steer the world to left by touching on the left half side of the screen or just the opposite.
While doing all of this hard stuffs to keep our world safe, you are going to be able to see the drift velocity and gravity on the top left side of the screen. The drift velocity is the velocity that basically defines the speed of our world's journey in the space.
On the other hand, the gravity is the force that makes our world so sensitive for steering.
Have fun and good luck !