System 1/2 (one-half) is a lightweight roleplaying game system meant for one-shot and pickup games.

You'll need two or more players to play this game, several six-sided dice, and some way to record notes. One of these players needs to take charge and setup the game's narrative. This player will take on the role of Narrator for the game. The remaining players will create Characters that are part of the game's narrative. From this point on we will call the narrative of the game the Fiction, to be concise. How these roles work and interact is the very core of the game, so let's explore that.

The player that becomes the Narrator takes over more responsibility than the other players. They game itself may often start with a player going: I have an idea for a game! In that case, they are the prime candidate for the Narrator. The Narrator paints the world, and the people within it, using words. They are in charge of pretty much everything about the setting of the Fiction. However, They may not describe anything about a Character that has not already been established, unless a game rule tells them that they may. The basic flow of the game is the Narrator telling the story of the Fiction, until a Prompt causes them to stop. There are a few types of Prompts, but the most common one is when a question is raised in the Fiction about a Character. Then the player of that Character and the rules are consulted to figure out the result in the Fiction.

As you narrate the game you'll need pencil and paper (or another recording medium) to record Issues. Issues are points to consider in the story that affect one or more players. Issues have types and interact in specific ways with the rules to affect the fiction. Issues can often raise special Prompts for instance.

Each player that is not the narrator will create a Character. A Character is one individual with a prominent place in the Fiction. I'm sure that you've read books and/or watched films, so you have a good idea of what a Character is in a story. The player of the Character is responsible for bringing them to life. You should treat your Character as a role you play in the Fiction. There are many ways to do this, from the simple approach of making a fantastical vision of yourself, to reaching the extreme of intentionally creating an individual quite distinct from yourself and exploring that imaginary individual. No way is right or wrong, and you should experiment and discover what works for you. The Character you create will take part in the story of the Fiction, as you choose. You aren't however the author of your Character's story, just a director. You decide what your character says and does, and even are allowed to create their history and sometimes how they fit into the Fiction. There is never a question of when your input is needed, the rules always clearly call for it. For instance, when a Prompt occurs, the Narrator will engage you and ask questions and using the rules eventually you'll be called upon to narrate your Character's actions and their results, adding that to the Fiction of the game.

As you play you will need pencil and paper (or another recording medium) to record Features of your character. These are important information about them which can influence the rules and therefore the Fiction itself. There are several types of Features and each has its own way of working in the rules.

The Fiction is a shared space in the imagination of the players. It contains the story of the game, and how that relates to the Characters of the player. Ownership of this imagined space lies mostly with the Narrator. Ownership in game terms defines control. The owner of the Fiction at any point has control over the game's unfolding story - what happens next in the context of the current narrative. The owner of the Fiction at any point can be defined very simply: The Narrator owns the Fiction until a Prompt causes that to be suspended. At that point the rules determine how things proceed, and eventually a player of a Character will assume ownership for a short period. At the resolution of the Prompt, ownership returns to the Narrator once more. There are many types of the Prompts, but the basic and most common one is when a question arises in the story about what a Character says or does.

A Prompt stops the narrative of the game, and triggers rules. You follow the rules, and eventually the Ownership of the narrative will switch between players. After the situation in the story is resolved that created the Prompt, control reverts back to the player who had it last. While this is usually the Narrator, it is possible the narration of a player in the game can trigger a Prompt, in which case the rules are consulted and another player takes Ownership of the Fiction. At the end of this, the ownership reverts to the previous player, and then eventually back to the Narrator.

The default Prompt is always triggered when the question of what a Character does or says arises. At this point the player of the Character can describe what they want their Character to do, and then the rules are consulted to see how to proceed. Often things will just go as the player decides, and the Prompt is resolved, and the control of the story returns to the Narrator.