Abstract. One of subjects, I am teaching, is descriptive geometry. Once, having plenty of free time, I invented and implemented (in Pascal) a computer programm, animating affinity and collineation, the basic mappings of a projective plane into itself in descriptive geometry. This short paper describes and demonstrates the variety of options I included into the programm. By my opinion, this was a real usage of a computer in the teaching process (as opposed to the static questionnaires invented by my colleagues at that time).