According to my glass cutter, it was impossible to make 4 prisms perfectly fit to one another. Thus they all have different hight and when they are placed on an ipod touch, the gaps appear between each prism. Although these gaps make quite intriguing effects, and theoretically the mock-up worked well, its size probably should be scaled down to the actual display size (70.5× 50.0 mm) instead of the current size, which covers the entire ipod touch (111.0 × 58.9 mm).
The reasons for this are; firstly, some part of the display ( black part) and ipod touch (silver part) get reflected and distracted the animation. Secondly, 4 prisms couldn't be placed perfectly stable and fell off from the ipod touch. Consequently, I already tipped the edge of a large prism and cut myself.
Design instruction by Professor David Hall