You can absorb other galactic bodies, but only if they are smaller than you, otherwise... they absorb you and you lose. As you move through the atmosphere you expend energy that makes you smaller, so it's important to act quickly. A simple tap of the screen gets you moving in the right direction, and two finger pinch action will expand/shrink the screen to give you a better view of your universe.
There is an Odyssey and Arcade mode and several different awards you can acquire as you move through the levels, each with a different objections. This can be a slow moving game that takes patience, so it may for everyone. But we found it a great way to pass the time. Along with being available for iPhone and Android, they also have Linux, PC and Mac.