To read this book, a very modest mathematical preparation is sufficient: knowledge of the rules of arithmetic and elementary information from geometry. Only a small part of the tasks requires the ability to compose and solve the simplest equations. Nevertheless, the content of the book is very diverse: from the variegated selection of puzzles and intricate tricks of mathematical gymnastics to useful practical methods of counting and measurement. The compiler took care of the freshness of the included material and avoided repeating what is included in other collections of the same author ("Tricks and Entertainment," "Entertaining Tasks"). The reader will find here a hundred puzzles not included in other books, and some of the tasks, such as croquet, have never been published at all.