Free planet software for linux

WW2D is cross-platform, free and open-source version of NASA World Wind software, see http://worldwind.arc.nasa.gov for details. WW2D allows you to explore Earth using satellite imagery, topographic maps and image from other data sources also providing large placenames and boundaries database and allowing you to install additional data packs for even more information about our planet.
In basic configuration WW2D uses images from Blue Marble (1 km/pixel), LandSat7 (15 m/pixel), USGS Topo Maps, USGS Digital Ortho imagery, USGS Urban Area imagery.
WW2D is designed to dynamically download needed data from internet, however you can download data you want for faster access and offline usage.
Main features:
- Cross-platform code
- BlueMarble, LandSat 7, USGS imagery
- World, US, Canadian, Norwegian, Swedish boundaries
- Large Placenames database
- Search and Quicksearch
- Semi-transparent layers
- Support for worldwind:// links
- Partial support for WorldWind data (conversion needed)

RSS-Planet is a custom marker file generator for xplanet which uses RSS feeds from news websites to plot the current headlines on a world map.

By default, Yahoo! News and CNN.com are supported, but other feeds that point to articles with easily-discoverable place names (such as the Washington Post) should work as well.

Planets is a simple interactive program for playing with simulations of planetary systems, released under the GPL. The project runs on Linux and Windows, and could doubtless be ported to your favorite flavor of Unix.
Planets was originally designed for kids, in particular, for my then 4-year old nephew who is fascinated by astronomy. The user interface is aimed at being simple enough that a fairly young kid can get some joy out of it. But the adults who have used it have found it to be pretty fun as well.
The code is not bug-free, and Planets is missing some significant features. But its pretty stable and is a fun toy to play with. If you do download it, please drop me an email and tell me about your experience with it.
Main features:
- Saving and loading of universes
- Infinite undo (erase last action) and goback (return to point in time just after last action). This allows for undoing mistakes and replaying interesting configurations.
- Traces of planet trajectories
- Two ways of dealing with planet collisions:
- merges, where the colliding planets are merged into one planet, and
- bounces, where the colliding planets are bounced off each other elastically. This itself comes in two varieties:
- force bouncing, where the force between planets is made repulsive at close quarters.
- true bouncing, where simple pool-table physics calculations are made to determine when planets collide, and compute the appropriate bounce from said collision.
- kidmode, a mode where the focus is (mostly) locked on the application, and interesting changes are initiated by merely banging on the keyboard. This mode is aimed at 1-5 year olds.
- Center-of-mass following: it is possible to follow the center of mass of a subset of the planets. Thus, if you have a sun-moon-planet system, you can have the view automatically track the moon-planet pair.
- Can display kinetic, potential and total energy of the system.
- Both the gravitational constant and the gravitational exponent can be changed.
- There is a simple control panel that makes it possible to see and change the simulation options.
- Zooming, panning, and centering on the center of mass.

GNU Robbo project is a game ported from the Atari XE/XL.

The player has to rescue Robbo the robot from an unfriendly planet and help him collect all the parts of a capsule so he can go to another level.

Ophiuchus is a multiplayer strategy game in a similar vein as the Master of Orion series.
Ophiuchus will go through many phases where it is a completely playable game and it comes with further features added on with each major release.
The reason for this is that it is quite impossible for me to create a fully-featured game in one go. Doing it in steps allows me to re-check the game for gameplay quite often. (This also means I get to play it a lot, which serves to keep me interested.)
I aim to eventually create a game of rather large proportions, but this may well take some time. As such, I am concentrating on the gameplay of the game first, on the assumption that while graphics improve and change, gameplay stays eternal.
The game map is a rectangular board of tiles. A tile may contain a star. Each star is orbited by a single inhabitable planet. Each player starts out inhabiting a single planet, and owning 10 units of money.
Each planet a player owns adds 1 unit of money to their treasury per turn. You may build spaceships at your colonies, which cost 4 units of money, and take 1 turn to construct. Spaceships move across the map at a rate of 1 square per turn.
If a fleet encounters an uninhabited planet, it will automatically colonise the planet. If you encounter a planet owned by another player, you can attack and invade it. Combat works on the simple principle of winner-takes-all.
Whichever side has the larger fleet destroys the other side. If you retreat from combat, that is, if you order your fleet to leave a system while another player orders their fleet to attack yours, you lose a third of your ships.
You win the game by invading all colonies held by all other players.
Enhancements:
- When multiple players arrive at the same uncolonized system at the same time, none of them can colonize the planet now.
- Previously, the player with the lowest ID got the planet, leading to an advantage to players with lower IDs.
- This was a problem especially in single player mode, when it gave a great advantage to the player over the computer.
- Attack commands now always give feedback.

Qonk project is a game I wrote to learn some SDL basics. The game is a small build-and-conquer strategy game with very simple rules. A complete game only lasts for a few minutes and can be a fun break away from work or whatever youre doing.
The setting of the game is a solar system of planets. Your goal is to conquer all of the planets in the game by sending ships there. Planets that are under your control generate new ships. Simple AI players are playing against you. As you gain more experience throughout the game, more AI players have to be kicked out of bigger solar systems.
The game is currently very much in beta. I published it however in order to see whether it compiles on other machines, and to see what reactions people had on its gameplay. The game engine itself is fully functional. A lot of things have to be added to make this a mature game (like menus and stuff), but since the engine itself works, Qonk is already very playable.
How to run
In order to change between levels, Qonk exits and parameters for the game and its level have to be entered from the command line. After a game, Qonk will tell you how to start Qonk again when exited. This is because Im too lazy to write a decent menu system (everyone who is interested, may add a menu system to the source), and only interested in hacking and tuning he game engine, its graphics and obviously, game play.
Rodolfo Borges provided a small shell script that helps starting the game, saving your current level, and moving to new levels automagically. You have to edit the file to change the path where you have installed Qonk before running it.
Qonk can be given two numeric parameters, the first denoting the number of planets in the solar system, the second gives the number of enemy AI players. Successive levels of the game are defined by two such parameters.
The first levels in the game are given by parameters (6 1), (7 2), (8 3), (9 4), (10 5), (10 6), (10 7), (10 8), (10 9), (11 10), (12 11), ... I managed to get to about (35 34) before I got bored with it and started over again. I have also managed to win a (100 99) game once. That was pretty hectic.
Although the game engine is prepared to run under different modes, the game always defaults to 1024x768 resolution, and goes into fullscreen modus to run qonk. (because of beta status)
How to play
You select ships and send them out to planets, to attack or fortify them. A ship that arrives at an enemy planet dies and kills an enemy ship, residing on that planet, along with it. If no enemy ships are based on the planet, you take over the planet. Planets under your control grow new ships for you to send around.
You control white planets and white ships. Colored planets belong to the opponent players. Gray planets are not controled by a player and can easily be conquered, once its resident neutral ships are destroyed (about 2-4 of them on each neutral planet).
There are two types of planets in the solar system. There are planets orbiting around the "sun" and moons orbiting around the planets. There are as many moons as planets in each solar system. Some planets may have more moons than others. A planet is expected to generate twice as many ships as a moon in the same amount of time. Some planets/moons build ships more quickly than others. Each ship also has a random speed.
Select ships by dragging your left mouse button. A ship can only be selected for an action if it resides on a planet. Use the right mouse button to send selected ships to the nearest planet to the mouse pointer. If you want to select all of the available ships, press A.
As you conquer more planets, more ships are built in parallel. Try to conquer as many planets as possible, so that many new ships are constructed and you can reign over the solar system.
There are some extra keys that can be used:
- While pressing E, the ships of enemy players are shown, so this is kind of a cheat button
- Press P to pause and unpause the game
- Press S to save a screenshot (screenshot.bmp) of the game

xplanets shows a simulation of a spacecraft flying through the solar system. With the controls next to the simulation screen you can control the simulation and steer the spacecrafts flight.
The following planets are visible:
- the Sun (yellow)
- mercury (gray38)
- venus (burlywood2)
- earth (blue2)
- mars (LightSalmon3)
Note that the sizes of the sun and planets are not to scale, though their distances are. Showing the planets to scale would mean that they wouldnt be visible. The solar system is rather big, after all.
The planet nearest to the spaceship is indicated with a red circle around it. Its relative speed and distance are shown in the data display.
The xplanets program uses the GTK+ toolkit. It has been built with version 2.2.1, so it should work with any version >2.0.0. It does not work with GTK+ 1.x anymore.