This video shows a recent version of it in action:

And this one shows a little bit of the build process to date:

The project had two key goals - to be as thin as possible (the frame behind the sign is 6mm thick) and to have no visible hinge at the bottom (achieved through a novel hinge mechanism using flexible tape and a interlocking V). This picture shows a cross-section with the cam open to push the sign beyond its tipping point, causing it to fall down, as well as detail of the interlocking V at the bottom: