Single Comment

The Advancer is an interesting piece.  I have used it, and pieces related
to it, in some of my own as yet unpublished variants, but of course,
credit rightfully goes to David as the first publisher of the idea.  The
page also contains interesting ideas about the strength of the piece and
mating procedure.  The last diagram is in error, though, because it shows
a blue advancer instead of a white one.