Spot the Difference (Puzzle 40)

Open Puzzle 40 and Puzzle 40b in tabs.

There is one substantial difference, and it's not obvious to the casual explorer. The exercise is to find it.

You will find it by exploring, modelling and comparing. You will find it by comparing sources. You will find it by asking me for hints. You will find it by asking me. You might aim your exploration by thinking what I could easily change in one place that leads to a non-obvious change in behaviour. You can probably think of more.

First person (to be sure of what it might be) gains kudos – and becomes a helper and hinter to the others, if they ask. Or maybe we'll all explore together, and so we'll find it together.

At the start of the exercise, we'll agree collective ground rules – how long we'll spend, how collaborative we'll be. We might also exchange individual handicaps – maybe you won't look at the source, or you'll only use specific tools.