The geometry problems colorfully inscribed on sangaku plaques that survive in shrines and temples throughout Japan have long fascinated those who appreciate the beauty of geometric figures and enjoy challenging puzzles. Aida Yasuaki (1847–1817) was one of the most prolific originators of the wasan tradition that produced them. Instead of presenting and solving problems using modern techniques, Unger presents Aida's own solutions, transcribing his calculations into familiar mathematical notation, highlighting connections between Aida's work and both the mathematics of today and aspects of Japanese cultural history.