What is an Inglenook Sidings puzzle?

The Inglenook Sidings is a classic railway shunting puzzle. Using three short sidings and a cramped headshunt (room for the locomotive plus three wagons), you sort eight wagons into a specific five-wagon train. The catch: you can only ever reach the wagon nearest the throat of each track, so a simple-looking sort becomes a careful sequence of pulls and pushes.

It's a model-railway favourite because it fits in almost no space yet never plays the same way twice: there are 6,720 possible trains to build. SHUNT turns it into a daily puzzle: the same layout for everyone, a new one each day, and it shows you the fewest moves possible so you can chase a perfect run.