We have set our aim on the development of an advanced artificial intelligence for the alien units, that guarantees a real challenge for every great strategist.
Free Movement Standard makes a unit's movements very real.
For example, if your soldier can't get inside a building due to aliens blocking all the entrances, do not worry. Go around the building and use a proper weapon, for instance a rocket launcher, to make an entrance of your own.
The third side in UFO:Extraterrestrials includes the police, army and civilians. The police keeps eye on everything that is happening in the cities, the army maintains it's bases and civilians mind their own business, such as shopping, dating, harvesting crop in the country, mining in the mines, or just trying to save their lives...