Message #2133

From: Melinda Green <>
Subject: Edge turning {3,7} IRP solved
Date: Thu, 10 May 2012 19:26:49 -0700

I couldn’t let Ed have all the fun, and since he hasn’t yet gotten to
the lovely {3,7}’s that started me on the whole IRP thing I felt I
needed to attempt it before he got around to them. These edge turning
puzzles are often fairly easy and this one was not a big exception. The
process involves a lot of "walking" of pieces along straight line orbits
to their destinations. They can never be moved off of these lines which
is what makes it easy but in this case it involves a lot of tedium as
most of the loops traverse 24 faces and there are 56 total colors to
solve. The set-up & restore functionality in MT can remove half of the
tedium which is nice.

I ran into what looked like an impossible parity problem at the end
where a couple pairs of edges were flipped. (See attached.) Those pairs
were on different orbits so they shouldn’t have anything to do with each
other even though they crossed. Eventually I decided to study the colors
closely and found that there were two identical cyan colors that I had
mixed. I may have changed a color long ago and didn’t realize that I had
created a duplicate. Changing one of them to black I was able to finally
finish it but not before adding perhaps an extra thousand twists before
figuring out the problem. My total in the end was 3,547 twists.

These orbits are really quite lovely in the way that they wrap around
the 3D structure and I am thinking of making a sculpture based on how
they interleave with each other. I am sad to say that I didn’t solve it
in 3D mode because that would be far too difficult without macros at
least. It was however useful to switch between 3D and hyperbolic modes
to more easily see how the different orbits intersect in a given region,
sort of like climbing a tree to see the lay of the land before heading
back to slog around at ground level. I encourage anyone interested in
these puzzles to check out this gem.