Gearlock is a logic puzzle about brass gears. Each gear shows a digit from 0 to 9, and above it the digit it needs to show. Set every gear to its target and the lock opens. The catch: gears are linked by chains, so turning one gear also turns others. This guide gives you a reliable method for solving locks, and for solving them in par.
The rules in one minute
- Digits wrap around: turning 9 up gives 0, and turning 0 down gives 9.
- An arrow from gear A to gear B means that whenever you turn A, B turns too, by the amount on the arrow.
- +1 turns B the same way as A, −1 the opposite way, +2 twice as far, and so on.
- Chains only push in the direction of the arrow. Turning B doesn't affect A.
- One gear can drive several others.
Every lock has a par
Par is the fewest moves that can possibly solve the lock, and the game calculates it exactly. Solve in par for 3 stars, within two extra moves for 2 stars, otherwise 1 star. A perfect solve also earns a hint, and your total stars go on the global leaderboard.
The key insight: order doesn't matter, totals do
A chain only moves the gear it points to; that gear's own chains don't fire. So turning A and then B gives exactly the same result as turning B and then A. What decides whether you solve a lock in par is how many times you turn each gear in total, not the order. That turns Gearlock into planning: work out the right number of turns for every gear, and the moves follow.
The method: plan from the drivers down
1. Start with gears nothing points at
Look for gears that no arrow points into. Nothing else can move them, so the number of turns they need is simply the distance to their target, going the shorter way round. Write those numbers down first.
2. Work out each driven gear next
For a gear with arrows pointing into it, add up how far its drivers' turns will push it (turns × the number on each arrow). Then the gear itself has to make up the rest. For example, if a gear needs +1 and its driver will push it +2, the gear needs −1 of its own.
3. Always take the shorter way round
Digits wrap, so −3 is the same as +7. Whenever you work out a gear's own turns, pick the direction with fewer moves. This is where most extra moves come from.
4. Big links and two-way pairs
Links like +2, −2, +3 and +5 move a child several digits per turn. A +2 link always moves its child by an even amount, so it can't fix an odd difference on its own; the child (or another link) has to make up the rest. Some gears also drive each other in both directions. Those pairs have to be planned together, because each one's turns change what the other needs.
Worked example
Three gears: A drives B with +1, and B drives C with −1. A needs +2, B needs +1 and C needs −3.
- A has nothing pointing at it, so it needs exactly +2 (2 moves).
- B is pushed +2 by A's turns, but only needs +1. So B needs −1 of its own (1 move).
- C is pushed by B's turns: −1 turn × −1 link = +1. C needs −3, so it needs −4 of its own (4 moves).
Total: 7 moves, in any order. Now notice the alternative for B: instead of −1, it could turn +9. That would also push C −9, but C would then need +6. That's 9 + 6 = 15 moves for B and C instead of 5, so the shorter choice wins easily.
Endless locks and the daily lock
Locks get harder as you go, with more gears, more chains and stranger links that wrap around in surprising ways. The Daily lock is the same puzzle for everyone, so you can compare move counts with friends.
Tips
- Undo freely. Only your final move count matters for stars.
- When stuck, write down how far each gear is from its target. It turns the puzzle into simple arithmetic.
- Save hints for locks where you've already found a solution but can't reach par.
Try a lock in Gearlock and see if planning from the drivers down gets you three stars.