A toy set of elements that can be fitted together so as to form a pattern or picture which comprises types of flat prismatic elements of different forms, in which the number of elements is greater than the number of types, which comprise the following elements types: a square element, a square element with a circular opening in the middle, two different square elements from which a corner region of a quarter of circle is missing, a quarter of an annular ring, a quarter of a circle, a rectangle, a half of a circle, a pair of symmetrical right-angled triangles, an isoceles triangle and an equilateral triangle; wherein the toy-set comprises at least eight of these twelve types of elements.