Sandbox for Movable Type provides a new template set based upon The Sandbox theme developed by Scott Allan Wallick of PlainTxt.org.
Sandbox is a rich and semantic html structure with many unique classes to style and layout the content of a website simply using CSS. The template set has inspired the creation of many Sandbox themes
Sandbox is best described on the PlainTxt site: http://www.plaintxt.org/themes/sandbox/
