Just to add that like those before me, it is one of my all-time favorite games. Very, very engaging.
Note that while it immediately appealed to me, it took me a few instances of having a go at the game before it actually clicked and I continued with it, right till the bitter end.* Always a matter of right moment and right place, isn’t it. And even then yes I did restart a few times to get everything “just right” (e.g., satellites mentioned above, though I forget all the details. It just takes a bit to get a feel for the mechanics.)
But so it must have sat there unplayed for say a year or two, first. Anyway to add it to your library for a fiver of pretty much any currency I wouldn’t think twice about.
*And including its Enemy Within expansion, what they don’t tell you – or at least I wasn’t aware of it – is that’s largely a Game+ replay. Rather than being a disappointment however, I found this one of the rare instances where that actually works and is worth your time, so play them both and in that order, and hopefully like many you’ll be thrilled all over again. It is essentially the same game, but now pushed up by several notches. And no, I think you’d be missing out by skipping straight to it, forgoing the first part.