AlienBlaster is a refreshing open source shoot-the-aliens game with various levels and an arcade mode. It is available on Windows, Linux, OS/2 & eComStation, Mac OSX (DarwinPorts), MorphOS and AmigaOS4.

It isn't seriously addictive like Battle for Wesnoth, but AlienBlaster is pretty relaxing in its own way. Personally I use it as a stress buster in Kick-some-ass mode.

The bottomline is that you get to shoot some alien planes and ships, till you get to the big boss and defeat him.

Cons:
1. It doesn't keep high scores in non-arcade mode.
2. There is no network mode.
3. There isn't any cross-fire. Deflected enemy missiles or energy beams never hit them back. Nor can you hit each other ion dual playing mode. This reduces the realism of the game
4. After sometime gets repetitive

Pros:
1. Simple to play but reasonably difficult to master last level.
2. The last level (Argh…) is always fun. It requires your attention and comes with more surprises.
3. The game is especially difficult with the light fighter. It is almost impossible to dodge the energy beams at Argh level.
4. There are two bosses, one more difficult than the other.

Tips:
1. You ability to increase skill level is limited by your fighter.
2. Find out what you cannot use for your fighter from Infoscreen. Don't go after them.
3. Kick-Ass Rockets, Hell-Fire Rockets or Laser do not increase in strength when you get more than one. Just get one and leave the rest.
4. Collect nuclear weapons at the cost of all other weapons. It can dramatically change the battle in your favor.
5. Keep at least one nuke for each boss. It helps to get rid of extra ships while you are fighting the boss. You should also use a nuke to get some respite in the Argh… level.
6. Always hit the bosses with Kick-Ass rockets. They inflict most damage. Don't use them otherwise. The lasers are almost as effective. However Kick-Ass rocket has a delay before it hits the target. This is very useful for the first boss as it moves around a lot.
7. Never stop firing your primary weapon. It never depletes. I think this is a weakness of the game.

You can download it here. It is also available in extras repository of Fedora.