Gear Train

Gear Train is a quick mechanical-reasoning puzzle. A row of interlocking gears is shown, the first gear is turning a known direction, and you decide which way the last gear in the chain turns · clockwise or counter-clockwise.

The one rule that decides it. When two gears mesh, they always turn in opposite directions. So the direction flips at every gear along the chain. That means the answer comes down to simple parity: with an odd number of gears the last gear turns the same way as the first; with an even number it turns the opposite way.

See the rule, then prove it. While you choose, only the first gear shows its spin. After you answer, every gear lights up with its rotation arrow so you can trace the alternation down the chain and confirm why the answer is what it is.

What it trains. Spatial reasoning and rule-application · holding a simple alternating rule in mind and following it across a sequence. A correct answer grows your streak; one wrong answer ends the run.

Part of the PlayMemorize family of brain-training games. Runs entirely in your browser, works offline as a Progressive Web App.