2x0ng: Procedural Puzzle-Action Adventure

Retro and art-game fans will love this.

2x0ng is a challenging action/puzzle game with procedurally generated levels. It is pronounced "TWO-zong", and is the sequel to David O'Toole's 2009 PC puzzler Xong.

2x0ng framebuffer examples

At its core, this game is a mashup. 2x0ng's design is a nonlinear combination of several different late 70s/early 80s home video games, combining related aspects of each into something new. In 2x0ng, you move a guy around the screen and shoot at enemies in all directions, as in Berzerk. The ball you throw ricochets and comes back to you, like in Tron Deadly Discs. You break colored bricks with the ball, like in Breakout. You transfer colors from one place to another in order to complete the level, similar to Revenge Of The Beefsteak Tomatoes. 

To reach the next level, you must successively unlock new areas by opening color-coded gates in the correct order. The levels are procedurally generated, so the game experience is different each time. Later levels are much larger than the screen, and feature substantially more moving/colliding objects than would have been possible in a real home video game from that era.

Downloads:

• 2x0ng 1.0rc1 for Linux
• 2x0ng 1.0rc1 for Mac OSX
• 2x0ng 1.0rc1 for Windows (32-bit) 
• 2x0ng 1.0rc1c for Windows (64-bit) 

More links:

• 2x0ng homepage
• Soundtrack

Code License: GPLv3

Content License: CC-BY-SA 3.0

Red Eclipse 1.4 and a missed birthday

Good news is that the long awaited Red Eclipse version 1.4 was released yesterday.
Read the announcement (with full change-log) here. Besides general polish the most notable features are:

• Vanity items and improved colours: dress up and frag with style.
• Visible legs in first person: know where you are kicking and parkouring.
• New and revamped maps: bringing you even more variety.
• Better viewing: level flythroughs, improved third and first person cameras.
• Better menus and other HUD elements: easier to see and read at a glance.
• New weapon: Mines add a new dimension to the existing gameplay.
• New mode: attack and defend in Gauntlet, competing for the most laps.
• Automatic demo recording: for those times you just have to watch it again.
• User Accounts: donate or contribute, and wear the in-game supporter badge.
• Improved weapon balance and gameplay rules, bugs fixed, and much more.

Especially the visible legs in 1st person view add to the parcour movements and overall the game feels much more "complete" now. Here are some impressions of a bot-match I had earlier on:

The bad news is  that we missed Xonotic's third birthday, but you can still congratulate here (where you can also read about some pretty cool updates to the game). To celebrate it, kojin made a nice frag movie:


Enjoy!

Are We Alone? Atmospheric 2D

Are We Alone screenshot: Safe on Earth

Let's Play Are We Alone?

Are We Alone - a space game where you travel from planet to planet, between star systems in search of intelligent life - has been released on Github under MIT license.

It was made for Ludum Dare 22 "alone" and is a quite atmospheric piece.

Code License: MIT

Content License: Unknown

Shunned Survivor: MMORTS Tower Defense

Defending your outpost in Shunned Survivor

Shunned Survivor Commentary Video

Shunned Survivor is one of the entries for PyWeek #15 September 2012 "One Way Trip".

In the genre mix between MMORTS, city building, economy simulation and tower defense game, you control an exiled human, with the apparent goal to get back to earth.

The interaction with other players is quite indirect. You can attack other player's bases and win the "data" resource this way, which you need to perform "research" actions. However, defeating a base does not change it, you simply get the reward and can attack again.

Shunned Survivor Server map

While researching, however, you need to perform in a tower defense minigame, during which your defensive towers can be destroyed. If you succeed, the research was successful. If not, you have to enforce your defenses and try again.

Even though quite a bit of the gameplay time is spent on waiting for resources to be generated by the various resource gathering buildings, I find this game very entertaining and highly recommend you to give it a try.

Code License: CC0
Content License: CC0

Free Orion 0.4.2

A few day ago a much improved version of the 4X space strategy game FreeOrion was released. Check out this cool set of introduction videos (Part 1, 2, 3):



Most notable additons:

• Very much improved, non-cheating AI. Sometimes experienced 4X players loose.
• Many GUI enhancements and shortcuts.
• Galactopedia expanded with game mechanics articles and many cross-links.
• Batch production of ships now possible.
• Improved sitrep notifications
• Reworked stealth and detection
• Almost everything has been enhanced, reworked, and better balanced.

So go and kick some alien butt ;)

Asylum: Free-as-in-Freedom Horror Adventure, Successfully Crowd-Funded

This is a guest post by Hythlodaeus on an interesting FLOSS game engine project, being developed by a professional games company.

ASYLUM video

I guess I should take a few paragraphs on this article to explain my stance on crowd-funded game projects. I've always been turned off by most Kickstarter game projects for a very simple reason: after personally inquiring a plethora of developers on their stance for Open-Source and Free Software, I was generally met with negative replies, half-baked excuses, bitter retorts or complete silence.

Now, although I recognize it is every developer's right to pick the license and the conditions for the usage of their own work, it strikes me as a very odd attitude for people engaging into crowd funding projects to be so unwilling to provide any other warranties to their prospective backers and future customers other than “we will make this happen if you give us enough money”. From this point, let's make something clear: pledging on a crowd-funded game project isn't exactly the same thing as buying a video game. From the backers' part it's an investment and a risk. It's about depositing your faith on other peoples' words, in hopes they will eventually deliver what they promised. When you buy a game, be it good or bad, you at least know that you're dealing with a finished product. When you pledge on a crowd-funded project, completion is only a possibility regardless of the campaign's success.

So, in my personal opinion, I've always thought crowd-funded game projects should strive to provide the level of trust they request from their backers. In this case,  that means allowing people to have access to the game's source code under a permissive / Free Software license, preferably starting right at the end of the campaign. Why? Simply because that allows for a tighter control of what's going on in the development backstage, and will allow every contributor to provide better feedback on the work being done. Raw engine code also gives backers something that can eventually be picked up and used for other personal purposes, if the project happens to fail for some reason.

With that said, let's talk a little about this project, which is, after all, what lead me to write this post. Asylum is the brainchild of Agustin Cordes, the Argentinian developer behind Scratches, a horror game that managed to get some degree of attention way back in 2006. The project aims to create a Lovecraftian-inspired horror point-and-click adventure game that will focus on an intense and immersive atmosphere, followed closely by engaging storytelling. From the trailer and screenshots provided so far, it seems like a rather professional endeavour, but for me the most pleasant surprise, was that the developer's in-house engine, Dagon, will be Free and Open-Source. On top of that, Cordes himself actually took the time to explain why he believes the engine should be free, and how such a decision aims not only to help preserve Asylum for future generations, but also to empower other indie developers by providing an open platform anyone will be free to use.

Asylum Kickstarter Video (Bonus)

Since there is no information available about specific licensing on the project page, I actually went on to ask the developer about which specific license was being used for the Dagon engine:

Me: Hello. I have one question regarding Dagon. You already stated it's going to be free and open source, but exactly under which software license are you going to release it?
Agustin Cordes: Hi! We're currently using CDDL but I'm expecting to re-license with the more popular MPL 2.0 very soon. Cheers!
Me: Fair enough. Do I have your permission to quote this conversation in a news blog about Free Software gaming?
Agustin Cordes: Absolutely! :)

“MPL” referring of course to the Mozilla Public License, which despite not being a strong copyleft license, it is both Free Software and GPL compatible. So perhaps Dagon can motivate a new generation of graphic adventure lovers to innovate upon the work started by Asylum. We can only hope future Kickstarter projects and indie developers adopt a similar perspective on Open-Source development.

With little less than a few days to go (I'm ashamed to say I only heard about this project very recently), Asylum is already fully funded, but if you still wish to contribute to this genuinely FLOSS project, or simply purchase the game for a special price, you still have a chance. Extra funding goals have already been set, and some additional rewards may also seem worthy to you.

The source for Asylum's engine, Dagon, can already be found here, currently licensed under CDDL (Thanks to Evropi for pointing this out).

Winter Shorts 2: Physica, SkyRiot, OpenMW

Physica screenshots

Let's play Physica - a hard casual platformer game played on Linux

Physica is a very simple casual platformer game where the goal is to drive a square through game levels from its starting position to his goal, avoiding hazards and without falling down.

SkyRiot screens

SkyRiot is available for free for Android on Google Play and was released under open source and free content licenses on SourceForge.net [forum post].

SkyRiot is a 2D flying shooting platform action game for Android devices. Fly a hoverboard and use an assortment of weaponry as you, an anarchist, single-handedly wage war against a totalitarian regime. Full 360-degree aiming along with total freedom of movement will keep you glued to your device for many hours as you blast your way across over 10 game maps.

OpenMW v0.21.0 Commentary

OpenMW 0.21.0 has been released. Changelog:

• Various dialogue, trading, and disposition fixes and improvements
• Torch flickering improved to better match vanilla Morrowind
• Fix for attribute fluctuation when infected with Ash Woe Blight
• Adjusted activation range to better match vanilla Morrowind
• Fixes for the Journal UI
• Fixed crash caused by Golden Saint models
• Fix for beast races being able to wear shoes
• Fix for background music not playing
• Fix for meshes without certain node names not being loaded
• Fix for incorrect terrain shape on inital cell load
• Fix for MWGui::InventoryWindow creating a duplicate player actor at the origin
• Added video playback
• Added support for escape sequences in message box and dialogue text
• Added AI related script functions, note that AI is not functional yet
• Implemented fallbacks for necessary ini values in the importer, unused in OpenMW as of yet
• Implemented execution of scripts of objects in containers/inventories in active cells
• Cell loading performance improvements
• Removed broken GMST contamination fixing mechanism

To unknown horizons to forge worlds...

I totally missed the rather big update of Unknown Horizons at the end of last month. The changes/updates are summarized by them as following:

• Completely new tileset
• New buildings: alvearies, barracks, blender, cocoa field, doctor, herbary, lookout, pastry shop, spice field, vineyard, vintner
• Many new graphics for existing buildings
• AI can now handle war and diplomacy
• Vast performance improvements
• New music track: Battle
• Tons of bug fixes
• Updated translations
• Much, much more

Yesterday there was also a new 0.7.0 release of the 3D Worldforge client Ember:

Worldforge 3D client Ember 0.7.0

Graphics are starting to look rather nice, right?

Last but not least,the recently open-sourced AgentKeeper got a dedicated sub-forum on our messageboards and is looking for contributors:



So, if you want to help out with this brand new jMonkey powered dungeon tycoon game, check out this nice list of video tutorials.

Various follow-ups

First off as a rather fast follow up on the last post:

• New version of Alien Arena out, boasting a 300% increase in render speed
• Small, bugfix release of War§ow out now

Otherwise, as previously mentioned, Garage Games has now also released their 2D game framework under the MIT license:



Their 3D game engine also saw some nice updates lately, however sadly their crowd funding push to port Torque3D to Linux fell (not totally unsurprisingly) short of their 30,000$ mark (with about 10,000$ pledged).

Various voxel engine ramblings

I have outed myself previously as not a big Minecraft fan, so take everything in this post with a grain of salt (as I obviously don't really understand that genre).

Anyways... recently this sub-reddit for open-source games was pointed out in our forums, and while it isn't really as lively as others (for example the Linux gaming one) it pointed out an new project called Iceball:

Pre-alpha Iceball screenshot

Seemingly made by people not happy with the recent commercialization of Ace of Spades, it's an all FOSS remake, those early development you can follow here (or on their Github page).

Now maybe the graphics are lacking on purpose (see disclaimer above), but I couldn't help to think: why for f***'s sake did they have to reinvent the wheel with their own engine instead of using for example Terasology:



Or Minetest, or the Ardorcraft API for that matter???

Ahh well, at least it made me aware that Terasology is still very much under development, and with its focus on DungeonKeeper & Dwarf-Fortress elements, it might actually become a game I would play (and doesn't make my eyes bleed :p ).

Speaking of which... the guy behind AgentKeeper released yet another nice video and graphics are constantly further improved as seen here.

DevCorner: Blender Game Engine

While Blender3D is one of the premier FOSS projects out there, its integral part the Blender Game Engine (BGE) is often belittled as not a serious game engine.

While the criticism is certainly not completely unfounded  and the integration of limited "non-programming" game code creation (via logic bricks) gives it a bit of a "RPG maker" image, it really is a quite interesting platform to work on it seems.
Ok, probably as of now the BGE is really more of a rapid game prototyping engine, but previous experience during the Yo, Frankie! project has actually shown that at least compared to some other well known FOSS engines, it is a serious contender (that Blender Foundation project originally started on Crystal Space, and after many problems was implemented in the BGE in a few weeks only).



So what makes it so interesting? Well for one there is the full integration with a creation tool (obviously Blender3D) so that getting your content into the game is only a matter of making it. No exporters or anything needed... it just works. Then of course there is the fully scriptability via Python, also integrated tightly. Basically you never have to exit Blender, and testing your game can be done right in the editor with one click (no compiling etc. necessary). Oh and did I mention the great physics capabilities via Bullet, also build right in?

In addition your created game will be immediately available on any platform the Blender Game player has been ported (all major desktop operating systems, with an Android port under development and a browser plugin, too). In addition you can choose to publish your game as a single .blend file, giving the users a direct access to all the source files of the game; a wet dream of any true FOSS game developer!
The tight integration with the GPLed Blender Player, has been a major source of discontent with the predominately propitiatory game developing users of the BGE however. Thus there now exists also a few options to encrypt your game and/or run it on an external engine that can be kept close source (but I will not go further into that here). 

You can find a lot of (sometimes really awesome looking: 1, 2, 3) game projects on the Blenderartists.org forum. Now as I said, most of it is sadly closed source with propitiatory artworks, but I also have the feeling that some simply don't know or care about the legal implications of their "freeware" game (which sadly shows that even many people who use a great FOSS tool, mostly care about the "free as in beer" aspect of it). 

One of the more interesting projects right now (which might or might not become a full FOSS game) can be seen in this video:



It shows the most recent work by Martinesh, who is basically BGE's resident game art guru. Two years ago we already featured previous awesome work by him, but sadly that Air Race project is by now canceled.
What he is now working on is however rather a show-case for the really nice new graphical features in the BGE which he and others are developing in the so called "candy" development branch (on his blog there are also more details and nice videos from some time ago).

Another cool recent project it the rewrite of the the logic bricks visual programming idea via nodal logic blocks called Hive.

While not completely integrated into Blender yet, you can already try it via an external editor (the created python code works fine inside Blender). There are also some tutorials and a documentation for it.
Since my programming skills also lack somewhat, I find that an interesting tool... however most likely it is rather a nice way to do some level scripting, than actually programming the real guts of a game with it.

So where can you get started with developing your own game using the BGE? Well, the blenderartists.org sub-forums are always helpful, with some nice beginners video tutorials linked here, here, here and here ;)
There are even some books available (this one in particular is quite recent, which is a plus given the fast development of Blender3D) and there is of course the official Blender documentation.
Oh and a good source of content is (besides our friends opengameart.org of course) Blender Swap (nice interview with one of the creators here).

If you have further questions please comment below or ask over at blenderartists.org!

Updates from AgentKeeper

I mentioned this nice new project that appeared on our forums some time ago already, and while the promised source-code isn't available as of yet, a new and quite good looking video was recently posted:



Now as you can see, it shares quite a lot of graphics with OpenDungeons, which is not completely dead either, but there is at least some discussion to "jump ship" as AgentKeeper is progressing much quicker (with it being a University supported project).
You can follow AgentKeepers progress here if you fancy some nice dungeon management simulator ;)

P.S.: Stay tuned for an new version of Red Eclipse early next week.

Ur-Quan Masters HD released

Happy new year everyone!

So today I found out about this really cool project to improve the graphics of the open-source (with freeware media) classic Ur-Quan Masters (aka Star Control 2):



Having played the SD version back in the day on my GP2X handheld (and it seems to be available for Android nowadays too ;) ), I can assure you that the game holds up very well to today's standards, with a really cool and funny story and awesome voice acting. Higher resolution graphics thus can only make it better ;)

So, NO excuses now... give it a try!

Some upcoming releases

Looks like we will get some nice x-mas presents this year:

A bit delayed but probably right on time for the Mayan end of the world, we will see a long awaited new release of Cube2:Sauerbraten. Read about the release announcement here. Hmm, I wonder if it has already Occulus Rift support...

Also on the FPS front, AlienArena is having a major engine update, with a claimed massive 3-4 times speed increase in BSP rendering and more VBO improvements.

Mars meets CounterStrike?

Furthermore they announce a new game-mode to be added soon, which tries to slow down the game-play of AlienArena a bit and add a more tactical appeal. Sounds a bit like selling out to the CounterStrike/ModernWarefare crowd to me, but lets see how it will play ;)

Last but not least, GarageGames has announced that after the recent FOSS licensed release of their 3D engine Torque3D (see latest updates here, sadly no working Linux port yet), they will also open-source their 2D engine!

And in fact it will not only be a source-drop, but rather a significant update including a merger of their iOS code with the rest of the Torque2D one.

Also no Linux port yet, but just as for the 3D engine one will hopefully show up sooner or later.

P.S.: In case someone has missed it: SuperTuxKart had a very nice new release recently, bumping it up to version 0.8. See a video of it in action here.

Video updates (various)

Today I let the videos speak:
First of all a nice FOSS bullet hell SHMUP, called Shmupacabra:



Taisei Project is maybe also relevant if you like getting killed ALOT (hehe, insider joke for q).

Previously mentioned Cube Trains (based on Frogatto) has reached version 1.0:



You can support the developer of this nice puzzle game by buying the Expansion-pack for 2 Canadian bucks or more! Another option to try and fund FOSS game development... maybe there will be some sales figures published at some point?

Next on the list: open-source engine reimplementation project Corsix-th:



You will need the original game for the non-free artworks though.

And last but not least: 0 A.D. got a brand new website: www.play0ad.com! Celebrating this they also made some nice video tutorials for total beginners:



Have a look at tutorial 2 and tutorial 3 also.

Signing off :)

Edit: Small interview with the 0 A.D. developers.

D3 BFG source drop, and new hosted forum

Hot off the press is the news that id software has released the source-code to their Doom3 remastered BFG edition. Have a look at the code here. It seems like Mr. Carmack has back-ported a few nifty things from idTech5, so this is potentially quite useful for upcoming idtech4 based FOSS games.

In unrelated news, I am happy to report that we are now hosting the forums for the nice off-road racing game StuntRally. Join the discussion here.

Old StuntRally screenshot, too lazy to find another right now ;)

One of the really awesome features of that game is the track-editor by the way... have a look at some awesome video tutorials here. Given the Techno-style music in these and the awesome spline-based tracks, I actually think that a WipeOut like modification of this game would really rock, join the discussion I started on that here :D

0 A.D. and Megaglest updates

Some assorted news from the FOSS RTS thematic area.

First of all, Megagest saw another somewhat bigger release (3.7.x), and someone also made a nice cinematic for them:

Sadly no news on the planned graphical update, as the merger with GAE seems on hold, but the new version adds a lot of nice usability enhancements.

Much more active on the graphics front is 0 A.D. on the other hand. In their recent development update #9 they talk about completely switching to their new shader based renderer, and the guy behind these renderer improvements recently gave a short interview too.

Some other interesting news include this recent forum posts of some modders trying to switch to the 0 A.D. engine for their modern warfare RTS called Rogue Republic.
Asset integration seems to work already as you can see here:

Rogue Republic assets in O A.D.

The thread over at the 0 A.D. forums has a few additional details, but no significant info on the FOSS status they are aiming at in regards to their media.
Never the less, it looks like it might become a RTS project to follow more closely.

Cinematic ZeroK trailer

Busy for a while moving... and the crickets take over FreeGamer it seems *chirp* *chirp* :D
Anyways, I am partially back in business, so a warm HELLO from East Africa!!!

So nothing much to report right now, except that there is a really nice cinematic trailer available for the FOSS RTS ZeroK (which is based on the Spring engine):

They also released a new version not all that long ago, so give it a try if you haven't so far.

Stay tuned, as I struggle to get into my regular FOSS-Games blogging habit again ;)

Engine reimplementation day!

This is a guest post by user Hythlodaeus, discussing GPLed video game engine reimplementations, and presenting several projects related to the topic.

I thought I should take some time to discuss in detail one form of project that has been sometimes featured here, on FreeGamer, and is generally quite popular in the FLOSS gaming world: engine rebuilds / re-implementations.

Rather than being wholly original projects or Intellectual Property-free clones of more popular games, engine rebuilds (also known colloquially as “engine clones”) are essentially an attempt to completely reconstruct and improve upon the features of a given original game, without going trough the trouble or replacing original game art assets and without creating a new whole, free-of-restrictions and copyrights IP. Thus, engine rebuilds merely reproduce the rules, mechanics, and game logic of the original game, while still being dependent on some other form of original data.

These projects frequently arise as a form of preservation: the need to ensure and expand compatibility of a proprietary game out of its original borders, and to make sure the target game will not only be able to run on future systems, but also to be ported to different platforms where it wasn't originally available, without damaging the profits of the original developers or breaking any form of copyright. Better than that, engine rebuilds are a great way to fully enjoy many video game classics in a purely free-as-in-freedom environment, while still rewarding the original developers by purchasing the original game. As of now, I have four particular projects under my radar which I would like to talk to you about.

VCMI

VCMI is an engine re implementation of New World Computing's turn-based strategy classic, Heroes of Might and Magic 3. It aims to replicate the original game, and introduce many new features that will make it a more pleasant and customizeable experience, as well as providing a platform for scenario building, mod making, and even the creation of completely new games.

VCMI has also been noted for its portability outside of the desktop computer environment, with some developers outside of the main dev team apparently creating an Android port, and other similar mobile versions.

With the recent release of version 0.90, and bordering closer and closer to the 1.0 release, VCMI is the brightest hope for the huge Heroes of Might and Magic fan community which still holds HOMM3 as its all-time favorite game in this long-running series, and whose official releases and reeditions tend to run poorly on modern operating systems, including Windows.

FreeSynd

The second project is the Syndicate reconstruction known as FreeSynd. For those that are too young to have ever played the original game, Syndicate was a dystopian organized crime simulator, in which the player controlled a team of cybernetically enhanced zombies (!!!) in a campaign to achieve complete global domination.

Syndicate was known for its fast-paced, guns-blazing gameplay, and, after many years since its original release, it's still highly regarded as one of former British developer Bullfrog's best titles. FreeSynd is currently on version 0.6, with updates oozing out slowly, once in every few months.

The goal of the developers is to replicate the original game as it was, when released, with further upgrades and improvements coming only after version 1.0 is finished.

At its current form, many missions can be fully played, but the game still has many bugs and much to is left to be made. However, as a fan of the original game, I still felt it was my duty to talk about it and maybe motivate some of you to lend some help to what promises to be a fantastic game. Naturally, you will still require the original game data to run FreeSynd.

NXEngine

Next up we have NXEngine. So far, I'm really surprised how come this one escaped most people's attention, especially at the FLOSS gaming sphere. NXEngine is none other than a free, open source recreation of the legendary freeware game Cave Story. Now the original game is not only freeware, it has already been ported to as many platforms you can shake a stick at (including GNU/Linux). However the game creator, Daisuke Amaya, AKA “Pixel”, always requested people in charge of porting the game to never share the source code, due to the deal previously signed by Pixel to distribute the game commercially. This, however, did not stop programmer Caitlin Shaw from rebuilding the whole game engine from scratch, requiring only for the user to download a copy of the original freeware version, and extract all art and music assets from its bowels.

As of the current version of NXEngine (1.0.0.4), the game runs flawlessly, even more swiftly than the freeware original. Having played both in their entirety, I can say the only slight inconsistencies going for NXEngine, are a couple of enemy attack patterns which are slightly different, and barely affect game experience in any way. All in all, it's Cave Story, running free-as-in-freedom. And that's a great achievement by itself.

OpenXcom

Finally four our fourth project, we have OpenXcom. Many of you might be familiar with the game it is based on, as it was considered many times as one of the best PC games ever made. OpenXcom is a full reconstruction of this great tactical simulator, once again aiming for expanded compatibility and a more stable, smoother gameplay, along with many improved features and mod support planned along the way.

If you disliked the Firaxis remake, maybe you should keep an eye on this one. It's pure, classic X-COM with all the rough edges trimmed, and even at its 0.45 release, it already seems like an impressive achievement. If you feared for the future of X-COM, fear no more. OpenXcom is here.

That's all for now! I'm sure there are other great engine rebuild projects around there, many of which have been discussed here on FreeGamer previously. Feel free to post your own suggestions or comment on this matter.

Open-source head-tracking

So unless you are living under a rock, you have probably heard about the new VR-google craze soon to hit every hard-core gamers cave (e.g. Occulus Rift). We talked about the FOSS engine getting Occulus support before, and now that id software promised to release the Doom3 BFG Edition source code too, it looks like VR in FOSS games will become quite common soon.

However, hidden in the (flight-)sim genre another quite nice system has been developed, using only a (sufficient frames per second) webcam:

The video is shot with FlightGear, everyones favorite open-source flight-sim. More details how to get it running with FlightGear can be found here, the system itself is not FlightGear specific though.

The source-code can be found here to be adapted to to your game (any 3D game that doesn't require too fast head-movement is basically suitable). The face-tracking is based on OpenCV, which will take some juice from your idling quad-core CPUs ;)

Less resource demanding are infrared LED tracker version, which do not need to follow a face and also work rather nicely in a dark room. For those, some propitiatory solutions have been available for some time, but you can also find Linux compatible open-source code for such a system here (instructions for FlightGear here).

Personally I was always to lazy to build myself a proper 3 dot LED cap, so I think the face tracking solutions are more convenient. If you are into non-FOSS games on the Windows platform, I can thus also recommend the partial open-source FaceTrackNoIR software, which supports quite a few really nice flight-sims, racing games and even FPS.