It's simple: Each of the two steel spheres has to end up in one corner of the piece of wood.

Here is an unusual hint to get your mind going! (ACHTUNG: SPOILERS!)

Starting on December 13., "Steel Spheres" will be on the floor at the Exploratorium together with many other new exhibits of our "Mind" Section!

The puzzle was part of the "Grenzenlos" exhibition I worked on at a German Science Center (Universum Bremen), where it already made for a great exhibit. Now I added a visual hint to it that really lets you have a look at your brain at work!

Steel Spheres is part of the puzzle table created by Diane Withmore of the Exploratorium CPE.