there are 3 different ways to solve using 8 parts. the 1 arm + all inputs combination seemed easiest to program, so i mocked this up at the beginning of the week intending to come back later to explore the other options--both of which should both be much faster. unfortunately, i got so frustrated with sum4 that it killed my motivation to work on this puzzle any further. so, unoptimised new solution 1 it will have to be