Laser cut Raspberry pi case yin yang / ying yang

My RaspPi Case - acrylic laser cut design

http://www.led-genial.de/Plexiglas-Gehaeuse-fuer-Raspberry-Pi

Deutsch unten !

This great design allows the use of several parts and can be assembled easily. Simultaneously there is no danger to break it.
The striking advantage of this design is the possibility to use colored plexiglass or acrylic.
With the popular kits for hobbyists that you can stick together the only material which can be used is rolled XT. Otherwise it will break because