What are we talking about?
GameTree Linux is the natural prosecution of a project called "Cedega" which is a linux gaming platform, supporting officially a restricted number of games. Actually, GameTree Linux is, as today, Cedega itself, being the same program with another name. Transgaming team promised to improve the client, but they are now concentrated on improving their GameTree TV system (see http://gametreetv.com/ for more info).
Well, now tell me about its features!
All right! GameTree Linux features improved graphic settings (it supports shader and vertex model 3.0) and supports directx and opengl without any trick. It has a beautiful and simple GUI.
As i said, GameTree Linux supports officially (which means you should never have issues running and playing those games) some games (see https://gametreelinux.com/games-list for the complete list), but since some games update frequently (for instance World of Warcraft), and the program doesn't update since a lot of months, there could be some problems right now running or playing some of these games.
I want it! Where can i download it?
You can download it checking out its official site (https://gametreelinux.com/), registering for free, logging in, going into "GameTree Linux Dev Center" section, choosing your distro (it supports now all Debian-based systems, all Fedora-based systems, Gentoo, Slackware and some other distros) and downloading the right package.
Yay! I installed it... So now?
Fine. The first thing GameTree Linux will do when you run it, is download the latest engines, some fonts and the compatibility list of all supported games. Done? Fine. Now, the next thing to do is run the diagnostics to see if your system can handle GameTree Linux. Do it clicking on "Run Diagnostics" in the main window.
I suppose you will pass all the tests, since this test just wanna tell you if you can run the program, not the games. Let's analyze now some useful options.
Setting the program
Under Settings -> General, you can set some general options like the default engine, the default windows version, the resolution (only if you wanna run games in a window), and some useful tricks. I suggest you to leave all the options as default, unless you wanna play in a window, or activate the Cedega HUD (if you wanna check how much RAM is used and the FPS count of the game you're running).
Under Settings -> Graphics, you can set all graphic options. Again, i suggest you to leave all the options as default, unless you wanna do some tests or you encounter some graphical issues in the game you're running.
Under Settings -> Audio, you can set all sound options. In my experience, i encountered a lot of issues making the sound work ingame. If you also encounter the same issues, try putting "default" in both "CTL Device" and "PCM Device" instead of "hw" and "plug:dmix". I will never suggest you to use OSS, since is an old sound devices, not used anymore.
Under Settings -> Joysticks... Well, it's simple. You can set your joysticks! Just click on "Detect" and the program will find your device that you can test, clicking on it.
Under Settings -> Membership, you can handle your membership to let GameTree Linux download the newest updates for you automatically. And, of course, if you navigate under a Proxy, you can set it here.
Under Settings -> Engines, there's something you will always deal with. This indispensable section let you download and install older engines, that will help you testing some old games which require old engines in order to work. Simply click on "Install engine", select the engine you want to download, and let the program download and install it for you.
Under Settings -> System, you can check your PC specs, copy it on a clipboard or making the program detect them again for you if you change something in your PC.