Letter Lock – a daily word puzzle with letter rings and gears

Letter Lock is a daily word and logic puzzle: concentric rings of letters turn on a dial like a safe lock, and you set them so that every spoke, read from the outside in, spells a word. The framed top spoke is the word of the day.

The twist is the gears: some rings drive others, so one turn can move two rings. Finding the words is half the job; the other half is planning the order of your turns to open the lock in as few moves as possible.

Every day brings one lock: five- or six-letter words on six spokes, with two gears.

How to play

1. Drag a ring around with your finger, or use the ⟲ and ⟳ buttons in the ring's row. Turning one position is one move, even when a gear turns another ring too.
2. The centre ring stays put; it holds the last letters of the words.
3. When a ring drives another, the driven ring turns one position the other way. It never works backwards. The selected ring has a yellow outline, the rings it drives a dashed blue one.
4. A spoke that spells a word lights up green. The lock opens when every spoke spells a word; there is always exactly one solution.

Tips

• Start with the word of the day: the top spoke holds the most common of the words.
• A ring that nothing drives can be set right away, and later turns won't knock it out. Set the driven rings after their drivers.
• Green can mislead: sometimes a spoke spells a word that isn't part of the solution.

Strategy

• Think in two layers. First crack the words: which letters can make words next to the word of the day? Then plan the route: set a driven ring last, since its driver would move it again.
• When gears form a chain (one ring drives a second, which drives a third), start at the front of the chain and finish at its end.
• Count both ways round: with six spokes, two steps clockwise land where four steps anticlockwise do.

History of the game

Letter-dial locks are old: cryptexes and vintage combination locks used rings of letters. Letter Lock is PlayWord's own game; the gears turn it into a logic puzzle.

Frequently asked questions

What is par?

The fewest moves that open the lock. Open it in par or fewer for gold, up to par + 4 for silver, more for bronze.

What does a hint do?

It spins one wrong ring into place, bypassing the gears, and keeps it glowing blue while it stays there. A hint is not a move, but that day earns no medal.

Is there always exactly one solution?

Yes. A program checks every lock: of all ring positions only one spells dictionary words on every spoke, and par is the true fewest moves.

What if I get stuck?

Tap Solution twice to see the answer. The lock closes for the day but doesn't count as opened.