The article presents the results of an experiment in which Excel applications that depict rotatable and sizable orthographic projection of simple 3D figures with face overlapping were developed with thirty gymnasium (high school) students of age 17-19 as an introduction to 3D computer graphics. A questionnaire survey was conducted to find out whether the students acquired the principles of the projection, found the lessons interesting and contributing to their technological knowledge, and found the topic motivating enough to continue with more complicated models. The results are discussed.