Puzzle mode documentation

"Svetlana A. Tkachenko" <[email protected]> Fri, 27 Feb 2015 22:47:40 +1100
Newsgroups gmane.comp.gnu.xboard.devel
Message-ID <1425037660.1591717.233204097.03DFCE53@webmail.messagingengine.com>
I do not see documentation for "Mode → Puzzle". What does that do?

-- 
Svetlana A. Tkachenko
Member of the Free Software Foundation
www.fsf.org  www.gnu.org