Traditional roleplaying games make the player responsible for the success or failure of one character in the game, and gives responsibility for the challenges, structure, integrity, and enjoyability of the game to the Game Master.[1. Yes, this is a huge simplification. Run with it.] Understandably, many players then decide that the point of the game is to seek out good things to happen to the character ("successes") and avoid bad things that might befall them ("failures").
In extreme cases, the player will do what Brand Robins calls turtling.[1. This is the best Actual Play report I've read, for any game, ever. It's an interesting short story in it's own right, too, and accessible to non-gamers. I highly recommend reading the whole post.] They make sure their character is safe from anything the GM might throw at them by creating a static character with no motivations, no relationships, and no hooks to give the GM a way to make the character's life difficult. And yet, the greatest desire of a roleplayer is to be handed conflict tailored to the character they've created. A player who turtles is undermining their own enjoyment.
Shock: social science fiction does exactly the opposite of this. Shock has the players (there is no GM) each create a Protagonist with conflict built-in. (Actually, there's nothing on the character sheet that isn't an element waiting to push the character off-balance.) At the same time, players briefly sketch an idea for an Antagonist to the next player to the left, who will be creating and running the Antagonist to the first player's Protagonist. The Antagonist's job is to make the Protagonist's life miserable. A Protagonist pushed to their limits—who changes, bends, and maybe breaks—is what makes science fiction stories so compelling. So it is with a game of shock.
Shock plays well as a one-shot game for an evening's entertainment. First the players sketch out a setting for play with Issues, Shocks, and Praxis scales. Issues are the sorts of things that we have always grappled with as a species or a culture: religion, art, identity, personal property, slavery, monogamy, totalitarianism, the definition of marriage, voting, warfare, environmental collapse, colonisation, childbirth... the list is endless. Each player chooses an Issue. It should be a personal or social concern that they want to see explored in the game.
Next the group brainstorms Shocks and picks one (or two, for a longer game) that fires all their imaginations. Shocks are the things that cause upheaval in science fiction: time travel, mind swapping, cloning, telepathy, interplanetary war, immortality drugs, wormhole travel networks, and so on. The Issues and Shock are placed on two axes, forming a grid where each Issue intersects with the Shock. The Pro- and Antagonists' stories are formed out of these intersections.
Good science fiction puts our own culture and humanity into contrast. It's not about the science (although it's often damned cool), but about what choices people make under those conditions and why they make them. Praxis scales determine what fundamental choices the stories are going to be about. Will they be tempted by the Seduction of dissolving their identity into the Network, or will they dive into it to foil the Antagonist's Blackmail attempt? Will the Protagonist choose Deception or will they resort to Brute Force? The two ends of a Praxis scale can be complementary approaches, or stark opposites. Two dark choices will give a grittier, more dystopian game where the Protagonists face distasteful dilemmas; one "light" and one "dark" pole will make the game more about high and low roads, and the sorts of characters that choose them or struggle between them. The players pick two of these Praxis scales, and these will be used to frame every conflict and will colour the entire game.
Players then create their Protagonists. A Protagonist consists of a character concept and name, three Features that describe them, two Links to people or groups (either positive or negative), and a Fulcrum number on each Praxis scale. The Fulcra range between 3 and 8: lower numbers make the Protagonist better at the first end of the scale, while higher numbers make them better at the other end. Setting Fulcra near the poles gives the player more control over the character's choices, while middling numbers makes them the sort of person who gets jerked around by fate.
Mechanically, a Link means getting a second chance in a conflict, and doing so risks losing or changing the Link somehow. Links exist only to be broken, changed, strained, and hurt, which makes for drama and interesting stories. Features have no mechanical effect except by their number (they determine how many dice you roll in a conflict), but are key to the fictional side of the character. They are big waving flags that tell the Antagonist player and the Audience what makes the character tick, and by extension what kind of play the player wants to see for their character.
A player's Antagonist is three different things: the player to their left, a specific character that is opposing the Protagonist, and the diverse forces that are upsetting the Protagonist's comfortable life. Notice that the Antagonist doesn't "threaten" to upset the Protagonist's life—they do. The real story is in how the Protagonist moves from their static beginning to the conclusion of their Story Goal, and the Antagonist is there to make it happen.
There's a few more details to it, and I haven't gone into the actual resolution mechanics. The point is that each of these steps builts layers of conflict and meta-plot elements into the game session. The players are invested in the creation of conflict, not in preserving the safe bubble of normalcy around their personal character. Both Protagonist and Antagonist players are pushing the Protagonist, forcing hir into situations where they have to make difficult and interesting choices. They create and complete, over the course of a few hours, a story arc that is meaningful to the players at the table. No turtles here.