Here are some excellent tips for the physics-based puzzle game Osmos, hosted by the game's music composers. The core mechanic of Osmos is that you control a globe of mass, and you can trade that globe's mass for movement, by kicking a stream of mass out in a various direction, trying to reach and "eat" other globes on the screen to get more mass. Controlling the game is simple, but winning it is another thing entirely. Fortunately, these tips should help.
And they also go a long way to showing just how complex and well constructed Osmos is. You can not only use your mass to propel your planet forward, but you can also propel other planets away from you, and even push those into other planets, causing a domino effect to your own advantage. And using walls is another big one. They can affect your movement strongly without costing you anything, which make the edges of the screen very valuable.