Not just playable games, but also games that are different from the usual stuff you see. Was there any hacking type games like Uplink before Introversion released it?
Darwinia was a shooter/strategy game set inside virtual world.
Even Defcon is unconventional. A game about nuclear war and mutual assured destruction with a retro asthetic.
Don't forget the soundtrack! It added a lot to the game atmosphere :)
This is a great example of how some well though out details can play a massive role. Would the game be the same without the soundtrack, with the sounds of crying and coughing? It still would be a good game but not THAT good.
You do realise that you are talking about the game with a work panic button built in, right?
Get your coworkers and boss involved, and then play it in "real-time" mode windowed over the course of a couple days. That'll keep engagement up.