As I mentioned in the title of my post, I bought here Earth 2140 beacouse of included DOS version. I also own a HD version from Steam. I am pretty sure that AI are diffrent in both version. I played few first missions (ED campaign) in both games and DOS version is much harder. For example, when you need to find BTTI in HD version, you can fight and win with enemy. In DOS version you can only hide and seek. What supprised me the most, there are diffrent mission in HD and DOS version! In HD you quite quickly see briefing room and you need to choose next mission/continent (I chose the one where you need to build two bio-centers). On the other hand, in DOS version there were more missions (I did't see any briefing room with continents so far). And i had to secure wellness of two scientists, and then there was a map with a river in the middle. Cheers, Chris