GK Lexicon I
A timeline is divided into Ages, each of which consists of a sequence of Periods (each usually decades to centuries long).
A Period has a general description, defining the conditions and circumstances of that time period.
Each Period is a sequence of Events. An event happens at a particular time (although it might last several years) and in a particular place (even if a large region).
Each Event can contain a number of Scenes. A Scene is very short chronologically, usually involving specific people, and comes about to answer questions posed by the goings-on at larger timescales. (NB: Usually Microscope has Scenes being roleplayed out, but for this play-by-wiki game we can probably just stick with having a single player write it.)
Each of these elements (Age, Period, Event, Scene) has a title, tone (light/dark), and short description. Elements of light tone are positive/desirable, while elements of dark tone are negative/undesirable.
The elements must follow a hierarchical order (Age > Period > Event > Scene). Elements do not need to have the same tone as their parent (e.g. it's possible for a light-toned Scene to occur inside a dark-toned Event).
Play will take place within a specified Age.
Although the timeline has its own consistent order, elements do not need to be added in order. You can go back and add a Period between/before two Periods that were created in a previous round.
All elements must lie within the boundaries of the Age in which play takes place. The Age starts off with two "bookend" Periods, containing the introductory and concluding Events which define that Age.
No element added can directly contradict any existing element on a question of fact. However, it is okay to call context into question and to introduce opposing elements within the shared universe.
Constructing the palette for the Age
The palette is a set of things which either specifically do not exist in the world during this Age (that would otherwise be expected), or which may exist (that would otherwise be unexpected).
All players can nominate items for the palette.
While "false" items in the palette must not occur, "true" items may or may not occur, depending on whether somebody actually includes them in the text.
One person is the "Lens" for a given round. The Lens gives a topic which is the focus for the current round. All elements added this round must relate to the focus in some way.
The Lens adds an element related to the focus. They can also add one sub-element of that new element. (e.g. if the Lens adds a new Period, they may also add an Event inside it).
Now each participant adds one element (related to the focus). The element added may be a Period within the Age in question, or an Event inside such a period, or a Scene inside such an Event.
Remember that each element has a title, a tone (light/dark), and a short description (just a couple of sentences). Larger elements are less detailed.
Players don't have to write their entries in any particular order.
The Lens adds an element to finish off the round (again, the Lens may also add one sub-element of that element).
One player chooses a Legacy (something notable about the round topic).
This player adds one more element (Period/Event/Scene) relating to any Legacy. They can use the just-chosen Legacy or one from a previous round.
Finally, the Lens for the next round is chosen.