Anti-Sway▶Play

Two pushes, half a swing period apart, and the load hangs dead still under the trolley.

How to play

You drive a crane trolley with a load hanging under it. Hold a button to push the trolley and let go and it keeps rolling, because there is no brake — stopping means pushing back the other way. The load swings like a pendulum and can only be set down when it is over the target and hanging still, so both the position and the swing have to be right at the same moment. Pushing straight to the target and shoving back to stop always leaves the load swinging, and waiting does not help because nothing damps it. The way to remove the swing is timing: split each push into two and leave exactly half a swing period between them, so the sway from the first push and the sway from the second cancel each other. Every load lengthens the cable, which slows the swing and demands more patience, while the target narrows and the clock shortens. Three misses ends the run and your score is the number of loads you set down.

Tips & strategy

The load is a pendulum, and a pendulum has one number that matters: its period, the time it takes to swing out and come all the way back. That period depends only on the cable length, not on how hard you push or how heavy the load is, and it is the clock the whole game runs on.

Here is why timing beats force. Every push you give the trolley starts a swing. If you give a second push exactly half a period after the first, the load is on the far side of its arc at that moment, so the swing the second push creates is upside down relative to the first — and the two cancel. The load ends up travelling with the trolley instead of behind it. Give the second push at any other moment and the two swings add up instead.

So the move is: push, watch the load swing out and come back, and push again as it passes under the trolley. Then to stop, do exactly the same thing in reverse — push back, wait a half period, push back again. That is four short pushes for a whole delivery, and the load arrives hanging dead still.

The measurements are stark. Pushing to the target and shoving back to stop sets the load down **never** — not once in hundreds of loads, because the arrival always carries a swing. Ignoring the load and stopping the trolley exactly on the mark works about one time in ten, and only by luck of phase. The two-push method lands it six to nine times in ten depending on the cable.

Two details worth knowing. First, the period gets longer as the cable does, so the same rhythm that worked on a short cable will be far too quick later — read the swing, do not count in your head. Second, if you arrive with a small swing left, do not try to chase it with little corrections; a correction is just another push and it starts its own swing. Wait for the load to reach the far end of its arc and give one push there, and you can cancel what is left in a single move.