Kandinsky taught the basic design class for beginners and the course on advanced theory at the Bauhaus; he also conducted painting classes and a workshop in which he augmented his colour theory with new elements of form psychology. The development of his works on forms study, particularly on points and line forms, led to the publication of his second theoretical book (Point and Line to Plane) in 1926. His examinations of the effects of forces on straight lines, leading to the contrasting tones of curved and angled lines, coincided with the research of Gestalt psychologists, whose work was also discussed at the Bauhaus.[12] Geometrical elements took on increasing importance in both his teaching and painting—particularly the circle, half-circle, the angle, straight lines and curves. This period was intensely productive. This freedom is characterised in his works by the treatment of planes rich in colours and gradations—as in Yellow – red – blue (1925), where Kandinsky illustrates his distance from the constructivism and suprematism movements influential at the time.