Put together a roadmap that shows how the various pieces are put together to make them work. Basically showing the dependencies of each piece of the puzzle and what they will enable.

Having a clean specification of the Box Model that layout specifications can target is an important prerequisite for exposing layout data and eventually allowing modification of that data.

Apart from inline style, The CSSOM is the only script-based point of access to CSS. At the moment it's underspecified, inconsistent across browsers, and missing critical features. We should fix this.

One conception of Houdini is that it will explain CSS & Layout on the web, in line with the Extensible Web Manifesto. This page is meant to describe some of the black boxes in CSS and sketch potential strawpersons for exposing APIs to these areas.