Mobile: balance a hanging sculpture

Alexander Calder spent a lifetime making sculptures that hang from a thread and turn in the air. Every rod in one is a little sum: the weight on the left times the length of the left arm has to match the weight on the right times the length of the right arm, all the way down.

Mobile is that sum, given to you as a thing to build. There is a sculpture with empty strings, and a tray of coloured shapes. Hang them so nothing leans.

How to play

Drag a shape from the tray onto any empty string. Drag it off again to put it back. The sculpture will swing, and then slowly settle to tell you what it thinks.

• Area is weight. The bigger the shape, the heavier it is. There are no numbers anywhere, and that is deliberate.
• Watch it lean. A rod tips toward whichever side is heavier. That is your only feedback, and it is honest.
• Wait for it to settle. A mobile takes a few seconds to say what it thinks. Rushing is how you get it wrong.
• There is exactly one right answer. When it hangs level, you did not get close, you got it.

Your progress saves automatically. There is no timer and no move limit.

Why it is satisfying

This is not a puzzle you deduce your way through. It is something you make, the way a person actually makes a mobile: hang a piece, watch, adjust, wait, adjust again.

The difficulty is real but it is a difficulty of the eye rather than the head. The shapes are irregular so that area cannot simply be read off, and a piece twenty percent heavier is only about nine percent wider. Tested against simulated players who see only what you see, an attentive one succeeds around three quarters of the time and a hasty one around four in ten. Notably, a player with an unrealistically good eye does no better than a merely patient one, which is the point: this rewards care, not sharp vision.

Tips

• Start at the bottom. The small rods settle the ratios that everything above has to work with.
• A short arm needs a heavy shape and a long arm a light one, which is the opposite of what it looks like it wants.
• If two shapes look the same size, they probably are not. Hang one, watch, then try the other.
• When a rod is nearly level, the answer is usually a swap and not a shuffle.

Frequently asked questions

Is Mobile free? Yes, completely free, with no account and no download, in any modern browser on phone, tablet or desktop.

Does it work on mobile? Yes. Shapes are dragged with a thumb and the sculpture scales to the screen.

How do I win? Every string carrying a shape, and every rod hanging level.

Is there always a solution? Yes, and exactly one. The balance conditions leave a single answer, so a level sculpture is always the right sculpture.

Do I have to be good at maths? No. There are no numbers in the game and nothing to calculate. You look, you hang, you watch it settle.

Enjoy something to build? Try Socket, Sluice or Bloom, or browse all Zamborin games.