The packaging is designed based on Gestalt theory :

Similarity (The figure-ground principle states that people instinctively perceive objects as either being in the foreground or the background. They either stand out prominently in the front (the figure) or recede into the back (the ground).
Figure-ground (The principle of similarity states that when things appear to be similar to each other, we group them together. And we also tend to think they have the same function).