Orbit is an addictive Open Source game that is based on a Newtonian physics simulation system. It takes some practice initially to figure out how to maneuver your spaceship when floating freely in space. To help you get started, the space bar can be used to stop at any point. It is also instructional. You can explore all the planets and their moons in our solar system and learn their names along the way. Their display is based on NASA images.

When playing Orbit, your are given missions, such as fighting aliens that are invading our solar system. You can also extend the game, if you like, and create new planets, moons, and solar systems. New missions can be added as well.

The game has multiplayer network support to allow you to compete with other spacemen over the internet. There doesn't seem to be a help function, but you can find the full documentation here. The options and settings you select during the game are stored in a preferences file. This file also contains other parameters, such as screen size, that you can directly edit in the file. After you install Orbit, the preferences file 'prefs.txt' should be in your home directory in the '.orbit' subdirectory.

For more information and download files, see here. Ubuntu users can install it from the Multiverse repository through the Synaptic Package Manager or the Add/Remove option under Applications.