Four identical pieces of brushed stainless steel that look almost too simple to be difficult — the Tetra Puzzle's challenge is assembling them into a tetrahedron, a task that's far less intuitive than it first appears. Designed by Revision for Craighill, it functions equally as a meditative brain teaser and a sculptural desk object.

At a difficulty rated 6 out of 10, it rewards spatial reasoning and patience rather than brute-force trial and error, and its weight and finish hold up to years of handling without wearing down.