Designed for travel, Microsoft's Surface Arc Mouse is flat and unusable in its resting state.

But when the user picks it up and bends it, it audibly snaps into its curved working shape.

This transformation also turns it on. It's a clever piece of design, now in its fourth or fifth generation, depending on how you count the iterations.

But just how does that bending mechanism work? I'd assumed it was some kind of snap-bracelet-type mechanism, which would require flexible metal bands. But when you listen to the snap made by the transformation, the sound is distinctively plasticky, ruling out the snap-bracelet theory. (You know that sound that a "sticky" Rubik's Cube makes? It's like a sharper version of that.)

As it turns out, the mechanisms that enable the mouse to hold two shapes is pretty complicated. An array of interlocking plastic parts, multiple metal sheets both above and below this array, and a magnet all work together to perform the trick.

In the video below, Mr Teardown demonstrates how the mechanism works. (I've cued it up to the right spot.)

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Definitely the kind of thing where ID came up with the concept, and ME had to figure out how to make it work.