Reading on email? The visualisations will work better in browser. My son is two years old, which means he has an Apollonian will to power and loves all kinds of mechanised transportation and earthworks machinery. His particular joy is “playing choo-choo” with a Brio wooden train set. Since he likes me to be involved, but I am expressly NOT permitted to touch the trains, I amuse myself by building interesting track layouts. After a long while, I began to think more systematically about Brio. The pieces are clearly designed to fit together into shapes, so what’s the underlying structure in the design? Given out set of pieces, what is the most elaborate layout I can build? I don’t have a formal maths background, but I could see that this was an interesting algorithms problem lying on the floor in front of me. As I explored this, my son demonstrated a hitherto undetected expertise in constraint solving. The rest of this post is a lightly editorialised account of what he told me.…