Inspired by something I saw on the forums, but can no longer find with a search, and by my grandson’s upcoming birthday, I designed and built a 3-D maze from 2.2 mm acrylic sheet. You drop the ball in the hole in the top, rotate the cube this way and that and finally – if you do it right – the ball comes out the hole on the maze’s bottom.
Here’s the prototype:

Once I homed in on the right tab dimensions to get a nice interference fit, it all went together very nicely. The prototype is just held together by friction and is quite solid. I plan to weld the final version together with solvent and filling the engraving with paint to make it stand out.