Crosswire

Sixteen letters are already on the board. Swap them until all four answers read correctly.

• —Four hidden words around the edge, and every letter you need is already on the board. Nothing tells you what they are but the colours.
• —Tap one tile then another to swap them, or drag one onto another. They do not have to be next to each other.
• —Every tile is coloured for the answers through it: green where the letter belongs, amber where the letter belongs in that word but in a different position, and plain where it belongs to one of the other two words instead.
• —The corners belong to two answers at once, so one of them settles two words.
• —Once you solve a word, its five letters lock in place and stop moving.
• —14 swaps for the whole board. Spend them all without four answers and the puzzle is lost.

Where to start

Solve the corners first. Each one is shared between two answers, so a letter you are confident about there settles twice as much as a letter in the middle, and a word that locks takes its five tiles out of your way for good. Then let the colours do the arithmetic: an amber tile is a letter its own word wants and has misplaced, so the swap worth making is the one that turns two ambers green at once, while a plain tile is a letter to trade away to another word rather than shuffle around inside this one. Work a corner rather than a word: it is the one tile whose colour is two answers talking at once, and it is where a board with nothing written on it gives itself away. Swaps are the thing you run out of, and the cheapest swap is the one you did not have to make twice.