Nuts & Bolts

Sort the nuts until every bolt holds one colour. A nut only moves onto its own colour — or an empty bolt.

Two empty bolts is fewer than it sounds, and the game punishes filling them early. Work out where a colour is going to end up before you move the first nut of it, and keep one bolt genuinely free for as long as you can. Undo is unlimited and costs nothing, so the honest way to play is to try the move and read what it does.