I happened on a twitter note advocated by Henry Reich of minutephysics.
I enjoyed it and I expect you might, too.
Frictionless blocks, lossless collisions, energy and momentum conserved -
in short, everything a physics student might value, with
a telling use of phase space (one of John Denker's favorite allusions)
and a predictor thrown in for free - a pi calculator to any desired
??precision.