This set combines the sun and moon design with the Yin and Yang.

The sun and moon keep with the tradition of opposite symbols on each ball, but they are characters with a blissful relationship.  They need each other for balance.  The sun represents light and hides when the moon, representing dark, is out.

The Yin and Yang are two symbols that represent opposing forces.  Yin represents the passive, dark, and negative forces while the Yang is the opposite representing the positive, light, and energetic forces. While they oppose each other, their characteristics are complementary aspects of each other because without Yin, there would be no Yang.