Been a while since I played the first Nexus game, never finished it.
It wasn't really hard, from what I can remember, but there was a game breaking bug that happened every time I played. Vaguely, I seem to remember that you get an alien ship, blow something up, and get teleported into space where you have to save a convoy or something. I could be wrong, like I said it's been a while.
Every time the mission would start, something would bug and everything would explode and I couldn't progress the mission.