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X-COM 2 or Terror from the Deep (TFTD) was published an released by Microprose in 1995. It plays 30 years after the first part, X-COM UFO defense. Instead of coming from Mars, the aliens now come from the deep sea, but seem to have been in stasis there a very long time.
The game is a pure singleplayer game, so LAN or network aspects are no matter.
Here's just a reduced version of the tech tree. This is basically a trimmed version of the original in the Complete section afterwards. If you know X-COM 1, you actually know how it works. If you want to keep the fun factor a bit longer the first time, the hint after the picture should be enough to not be totally frustrated. For someone who doesn't know the first part, the tech tree shouldn't matter. At least once you should have played X-COM 1 or 2 without hints.
Essentially, that's all that's somehow important for the game. Note: without the “Deep One Terrorist” you won't be able to knock anything off. In the very first terror mission there is always at least one of them. If you miss it, it can take quite a while (and delay progress) until you have an opportunity again.