Four meshed gears form a chain, each spinning at its own speed off the driver gear at the front. Drag left or right to spin it up — the output gear's speed shows on a dial with a green target band. Keep it inside that band and a sync bar fills toward completing the target; spin too fast and the whole chain grinds to a jam, costing a life. Every target you sync raises the next speed and narrows the band, so easing off cleanly matters as much as spinning up.
Spin the gear chain to match each target speed in time.