Robert Lang, one of the world's foremost origami artists and scientists, presents the never-before-described mathematical and geometric principles that allow anyone to design original origami, something once restricted to an elite few. Existing origami aficionados will find previously unpublished models such as the "Black Forest Cuckoo Clock." Origami novices will appreciate the organization of Origami Design Secrets, which begins with easy techniques and progresses with straightforward algorithms for intuitive, concrete examples like rivers, packing of circles, and assembly of tiles. An appendix includes the advanced mathematical concepts. From the theoretical underpinnings to detailed step-by-step folding sequences, this book takes a modern look at the heart of the centuries-old art of origami.