I'm trying to codify the goals that I want to accomplish with
  Rebirth. This mostly encompasses guiding design principles,
  priorities, etc.
  
  In rough order by priority, descending:
 
    1. Ease of use. It should be natural to express game behavior,
       without needing to jump through hoops. Use of defaults and
       constraints to suggest a course of action and reduce the
       "burden of choice" on developers.
  
    2. Flexibility. Rebirth should be able to handle games of many
       types and genres; physics or non-physics, action or slow-paced.
  
    3. Object-oriented. It should focus on game objects and how they
       behave and interact, not on the mechanics of image blitting
       and event management.
 
    4. Examples. Plenty of running example games to help users get
       started and see how the library can / should be used.
 
    5. Documentation. Every module, every class, every method
       documented, plus tutorials with examples about various important
       concepts and features.
 
    6. Behavior-driven development. Spec first, then implement.
       Full spec coverage, master branch is always green.
 
    7. Small, incremental releases. Every feature should be a release,
       every release should add or refine a feature. Avoid build-ups.