Made from wood in two different tones and acrylic. Nearly half of the tray is covered in acrylic and you only have the other half to shift the pieces around. The goal is to find a way to place the extra T-piece alongside the other five. Extra challenges include packing the pieces in such a way they cannot slide inside the frame. Then try to do the same thing with five pieces, then with four pieces and finally with only three pieces. A fascinating puzzle by Jürgen Reiche.