The package allows manipulations of any LuaTeX document (it is known to work with Plain LuaTeX and LuaLaTeX). Most of the package’s functions are merely for fun or educational use, but some functions (for example, colorstretch for visualising the badness and font expansion of each line, and letterspaceadjust doing what its name says) could be useful in a “normal” LuaTeX document.

The author is Arno L Trautmann. The package is Copyright © 2012-2013 Arno L. Trautmann.