This is a collaborative writing 'past-time' in which the story line remains linear and writers do not have personal characters. The rules are simple:
1. Each additional post can only build on what has occurred in the previous.
2. New characters cannot arise unless potential candidates have appeared in the previous post.
3. Once a new character has been established the story can then follow their life if the writer so chooses and another writer cannot continue to write from the perspective of a previous character if they are no longer in the current setting.
4. You can only write and expand upon the current setting, which can be made as narrow or wide as one sees fit.
Simple, eh? Believe me, the story can get written into a corner really fast, the goal is not to let that happen.