A while back I saw The Illusionist on DVD. I was immediately captivated by the puzzle locket that appears in the film. Would it be possible to build such a contraption? I concluded that it would be and wrote a a couple of posts about it (here and here) on my blog. Apparently, I wasn’t the only one interested in the locket. My blog traffic tripled after that from Google hits on the subject.

Here’s the movie clip showing the locket in action:

Well, give the people what they want is my motto. I thought it would be interesting to create an animation showing how such a locket would work. First of all, I had to realize that there was a difference between saying “oh, I think that could be done” and actually figuring out how to do it. After a few days of obsessing, I got what I think is a workable design and made a brief (and very rough) animation illustrating it. Before posting it, I wanted to give you all a chance to solve the problem. As is often the case, working on the problem is more fun than hearing the solution.

Some guidelines when you’re working on a design:
1. When the locket is not in its heart configuration, the lid should be fixed tight.
2. When the locket comes into heart configuration, the lid should be able to slide open.
3. The lid should open from the bottom/middle of the heart shape.
4. Bonus points if you can restrict the twisting movement of the locket to 180 degrees, and the lid open to 90 degrees.
5. Extra bonus points for simple and elegant design that might conceivably be carved in wood (by someone who would have to be really talented.)

Have a go at it… it’s a fun problem. I will post a link to my animation in the next couple of days.