We were done all installations and everything was working but we faced an unexpected problems. Projected images on the cubes were not clear because of reflections so it was really hard to recognize what images showed. In fact, you can see the projected picture on the cube, but it was not enough to play this puzzle. But we still wanted to keep clear plastic cubes to show bits. So we were looking for some suitable materials, we decided to put vellums on the top of the cube. Vellums were really helpful to get an clear image. And the images projected on the vellums looked good! We were satified with this.
An image without vellums.
And we put vellums like a picture, we got more clear and beautiful images on the cubes.