An introduction for readers with some high school mathematics to both the higher and the more fundamental developments of the basic themes of elementary mathematics. Chapters begin with a series of elementary problems, cleverly concealing more advanced mathematical ideas. These are then made explicit and further developments explored, thereby deepending and broadening the readers' understanding of mathematics. The text arose from a course taught for several years at St. Petersburg University, and nearly every chapter ends with an interesting commentary on the relevance of its subject matter to the actual classroom setting. However, it may be recommended to a much wider readership; even the professional mathematician will derive much pleasureable instruction from it.