was an American abstract painter. Many of his best-known works are characterized by orthogonal geometric forms that reflect his strong interest in the De Stijl movement and the work of Piet Mondrian in particular. For Diller, abstraction was the ideal realm of harmony, stability and order in which every form and spatial interval could be controlled and measured. His style began with forms of modernism, including cubism, Kandinsky's abstraction, constructivism, and other European models. He simplified his palette to the bold colors and black and white of neoplasticism and reduced his visual vocabulary to squares and rectangles.