The first playable should answer a question.
A prototype becomes more useful when its purpose is small enough to test and clear enough to disagree about.
Studio journal
NOTES FROM THE PROCESS.
Thoughts on building worlds, making games, and doing the work together.
Build the world into what the player does.
A setting becomes more memorable when its character lives in the player's actions as well as its stories.
Find the cooperation before adding the complexity.
Start with a reason to notice another player. Then discover what the systems need to support.