The Book of Changes (also known as the "Canon of Changes", "I Ching", "Zhou I") is one of the oldest known literary monuments. The oldest part of it, which is used in fortune telling, traditionally dates from the seventh century BC. Around the second century BC, the Book of Changes was adopted by Confucian tradition as one of the canons of the Confucian Pentateuch.

The book, in the form in which we know it now, was formed in the era of the Zhou Dynasty and consists of 64 descriptions of hexagrams (figures of 6 lines). Each hexagram describes a certain life situation in terms of its progressive development over time. The hexagram consists of six lines that can be solid (active, bright, yang) or interrupted (passive, dark, yin). Each hexagram (and each line in the hexagram) in the canonical text corresponds to a set of aphorisms, which should give clues to the answer.

Fortune-telling itself consists in choosing six features that will determine the hexagram-answer to the question of the fortuneteller. Traditionally, complex pseudorandom procedures with yarrow stems, rice grains or fortune telling stones have been used for this. Another way to get the features of the hexagram is to use three coins, this method is presented in the application offered to you.