Mathematicians, crystallographers, engineers, chemists, and physicists were among the first admirers of Escher's graphic art. Escher felt closer to people in the physical sciences than he did to his fellow artists because of the praise he received from them. Some of Escher's artwork was done more like an engineering project using ruler and compass than in a free spirit mode. Mathematicians continue to promote his work, and they continue to use his periodic patterns of animal figures as clever illustrations of symmetry.