Re-posting of an article first posted in September 2008.
You are an officer, say a commodore, in the military-diplomatic-exploration organization of an interplanetary nation with United Federation of Planets (UFP) membership. You've been tasked with asserting your nation's interests with respect to a certain out-of-the-way planet that happens to be rich in natural resources. Unfortunately, it's already inhabited, by a race of disgusting natives we will call the Filthy Humans.
Now, it would be easy to just send in the Space Marines and kill all the Filthy Humans; they have no technology comparable to yours. But you're under the watchful eye of the UFP, and you can't get away with actually doing that. Furthermore, there are several other nations much like yours, with objectives much like yours, and they are eager to take control of the planet before you can and to snitch on you to the UFP if you do anything illegal. So nobody can directly massacre the Filthy Humans; instead, you have to provide them with "aid" in the form of technologies they can't really handle properly, and hope that they destroy themselves. Ideally, you want to blame your own illegal acts on other interplanetary nations and get the UFP to give them grief instead of you.
So: the winning condition is that you're still in the game when the Filthy Humans destroy themselves. More than one player can win and it can even be a fully cooperative game if the players agree to play that way. The losing condition is that the UFP passes a resolution condemning your actions and you're forced to withdraw from the planet (in which case YOU lose), or that the Filthy Humans achieve commercial-grade interstellar spaceflight and apply for UFP membership themselves (in which case EVERYBODY loses).
Game play is simultaneous turns. On each turn the different groups of Filthy Humans tell you what technologies they want, and you have a limited number of actions you can spend on giving particular technologies to particular groups of Filthy Humans. You might or might not give them the ones they asked for. The relations of the different groups towards you will change over time according to their relations with each other, your responsiveness to their requests, and so on. Some of these technologies are illegal (or at least, illegal for you to provide to a low-tech civilization), so you have to consider covering your tracks if you hand those out. It may be especially amusing if the Filthy Humans manage to develop an illegal technology under their own power and the players blame each other. Other technologies may be non-obvious, so that the Filthy Humans will not know to ask for them even though they'd be greatful for those technologies if they were volunteered. Much of the game play comes down to careful decisions on which things to give to which group of Filthy Humans.
But you can also spend your actions on dirty tricks - such as false-flag operations, where you send your Space Marines to rape the natives and mutilate their livestock while disguised as agents of another player. Or you can request a visit from the UFP Inspection Team and hope they find evidence (real or planted) of someone else's misconduct and no evidence of yours.
After everyone has acted, the Filthy Humans have a chance to do their thing for a while, and then it's time for another turn. As the Filthy Humans accumulate more and more cool alien technologies, they'll start using them in their own local wars, and presumably reduce their own population over time, bringing the game closer to the eventual goal of Filthy Human extinction. On the other hand, the Filthy Humans will also be working on developing their own technologies with the knowledge acquired from yours, and if that effort gets as far as commercial interstellar flight, the game ends. So there's a constant balancing act for the game as a whole, and incentives for players to conflict with each other over threats to that balance.