This book briefly describes the holistic process of creating applications for smartphones and tablets. It discusses the features of mobile operating systems and devices, the choice of development tools, the preparation of working documentation in the spirit of Agile, the design of the structure and architecture of the solution, the creation of an automated pipeline Continues IntegrationContinues Delivery, as well as monitoring the performance of the final product on the devices of real users. All examples are in C #. The publication can be recommended for both experienced and novice programmers interested in developing mobile applications. It can also be used as a benefit in universities, centers of additional education, etc.