concen.icn: Program to play solitaire card game Concentration

usage: concen [winoptions] [ncards]

   Concentration, as presented here, is a simple solitaire game.
When the program starts, there are 52 playing cards, face down.
They may be turned over by clicking on them with the mouse.  Only
two cards may be face up at a time; if they are the same rank
(e.g. two sevens), they are removed.  The object is to clear the
table.

   (For an interesting discussion of two-person Concentration, see
Ian Stewart's "Mathematical Recreations" column in the October,
1991, edition of Scientific American, entitled "Concentration:
A Winning Strategy".)