Editing XCOM (section)

==UFO: Alien Invasion==
The most detailed opensource version of XCOM based on the Quake 2 engine.

Buildings are not destructible and it doesn't have a great fog-of-war.  It doesn't have unmanned vehicles like the current iterations and sadly doesn't have any sort of Chryssalids yet.

Has a better world map than any other XCOM in that you can fully explore it like google-earth, even showing ship movement on the globe in real time.  The campaign is more forgiving in that it does not force you through Acts like Enemy Unknown where you can't possible keep everybody happy, or has nations constantly bitching at you for radar coverage like in Xenonauts.  Instead you get to bid captured UFOs and give preference to unhappy nations that feel neglected or where you haven't been saving civilians frequently.  

The camera is completely free in battlescape mode just like in Enemy Unknown, complete with zoom capabilities.  Lots of different weapons, though you will find yourself a fool if you don't immediately start using alien weapons.  Also levels tend to have more floors than other iterations, such as one mission in which you're going through an office building or another where you're entering a subway.

The only major problem with the game is that the smoke grenades are so overpowered your guys will be coming out of your drop ship like Snoop-Dogg out of his trailer.  Otherwise you'll find aliens are more than happy to shower your guys with plasma from across the map.

After a general huge update smoke is now useless and aliens are much, MUCH more powerful. 

Oh, and its free. Still, fuck it. Final version is broken, often locking the game, and developers have lost interest, and no one picks up the game...Even though the Ufopaedia is far more detailed than the entire series and has hard-science explanations for equipment.