The traditional classification of educational programs into distinct "types" is no more useful. Therefore, each of our programs may have, for example, not only a simulation character but also a database content, tutorial aspects, a play element, etc. Whenever possible, we have tried to combine these different aspects and functions.

     Most of the software was programmed by university students. That justifies the non-professional presentation of some of them. The interface of our first programs (made six years ago using languages as Pascal, Basic, etc.) is naturally more poor than the modern ones (using Borland C++, Visual Basic and, more recently, Delphi). Pedagogic arguments and scientific accuracy have been combined in our software development and testing, since we consider them to be more important than, for instance, design. The oldest programs, in spite of their poor interface, keep interesting and are still being demanded and used by many schools. That interest may be also explained by the lack of up-to-date hardware by many schools. On the other hand, the most recent productions (the "Multimedia Periodic Table" or "Le Chat 2.0") have a commercial competitive look.