If you’re looking for a little variety to your daily shootouts, then it’s definitely worth taking a look at what kind of games the Open Source space has to offer us these days. And we’re doing just that and bringing you this series of what we think are seven great first-person shooters - all open source, all 100% free to download and play. Seven days, seven games. Let’s jump right into it, shall we.

#1: Tremulous

Visually, Tremulous is no UT3. But it offers a great amount of unique fun regardless.

Tremulous is a futuristic multi-player FPS built on the Quake 3 engine. The game pits aliens and humans against each other in a unique manner whereby both teams are required to build a base or at least key elements of a base to survive. The objective of the game is pretty simple; kill all opposing units and destroy their spawns. This however, is not always a straightforward process as good teams will have dedicated people building the base and repairing it as damage is created. Each side has two main character roles - builders and attackers (you can interchange between the roles as you feel the need). So there are definitely tactics involved if team members are properly communicating and working together to beat the other team.

The most unique gameplay element of Tremulous is that aliens can generally only attack humans at close range using melee attacks, whereas humans are able to attack aliens at long range with weaponry ranging from blasters to pulse rifles. Add in the fact that certain alien units can climb walls, and you have a rather interesting mix of gameplay.

Tremulous also has a 3-stage system where going up a stage will make the player more powerful. That means unlocking better weapons if you’re playing as a human, and evolving into stronger and more powerful units if you’ve chosen to fill the boots of an alien. You advance by killing opposing units, with the amount of kills required to go up a stage being proportional to the number of players on your team.

Slaughtering the opposing team also earns you credits (humans) or evolution points (aliens) that you can then use to upgrade your character either by buying new weapons or evolving into more powerful units.

The current version (1.1.0) is a standalone version, meaning you do not need to have Quake 3 to run the game. Official builds for both Windows and Linux are available, as well as an unofficial Mac build. There are always servers available and people playing, so there’s really no reason not to check it out.