Two buttons, that's all you need.
The premise is simple: absorb planets that are equal to or smaller than your planet. As you grow bigger, it becomes more difficult to avoid the gravitational pull of the larger planets and to attempt to steer clear of them (a lost life). Once you reach the size of the "exit star" it will glow a bright orange and then you simply induce that star to orbit around your planet and the level then ends. Any smaller planets which you chose not to engulf but got to enter orbit around your planet are worth a free turn in the subsequent levels (I was able to get 10 planets to orbit mine once, but in the following level I died at least 8 times, so I needed every one of them).
The graphics are very minimalist and the audio is equally subdued, but they are exactly what need to be. The modeling of the gravitational forces is very believable and eventually becomes second nature. I wish that the motion trail beyond the player's planet was a little more prominent as it gets difficult to ascertain how the gravity is changing the trajectory - but that a minor gripe.
For $6, there is nothing that compares to this game on WiiWare. It's a tremendous value and a serene diversion for any player - casual or hardcore gamers alike. Fun is fun, and that's all that this game exudes.