pkg://xabacus-7.3.1.tbz:99086/+DESC  downloads

This is abacus for X Window System. Essentially, this is a proof
by induction that a computer is more powerful than an abacus, since
a computer program can contain an abacus. (But then again, you can
simulate a computer within a computer, so what does that show).
Actually, with a real abacus, one can move more than one row at a
time with 10 fingers.  But on the other hand, a real abacus does
not have the current sum displayed as an integer.

WWW: http://www.tux.org/~bagleyd/abacus.html