bold colors and black and white of neoplasticism and reduced his visual vocabulary to squares and rectangles." "Diller developed a highly personal language based on three major compositional themes. These themes, which he labeled “First,” “Second,” and “Third,” explored the picture plane in relation to forms in movement and forms in constant opposition." "By 1934 Diller had likely become the earliest American exponent of Mondrian's type of geometrical abstraction." "In the early 1940s, he began creating wall-mounted wood constructions, and during the 1950s and 1960s his sculptures developed into the large-scale, free-standing, formica works for which he is well known." The Sullivan Goss Art Gallery notes the following about Diller's style: "Composed predominantly of squares and rectangles and accented with primary colors against a solid white background, Diller's mature abstract paintings are the result of his explorations of pure color and form. Diller's austere work recalls the stinging isolation of the lives of all Americans of the Depression era, and possibly his own. However, the well-planned geometric nature of his paintings reveals his desire for a reconstructed world prevailing over the seemingly hopeless situation in the United States during the Depression." Projects In 1934, Diller served as Supervisor for Mural Painting for the Temporary Emergency Relief Administration (TERA). The following year TERA was replaced by the Federal Art Project (FAP) but Diller kept his position as supervisor. He held this position until 1940. During his tenure at the WPA, "Diller championed abstract art and oversaw the execution of more than 200 public murals, most of which were completed as part of this large undertaking". "In the late 1930s, he supervised the artwork for the Williamsburg Housing Project in Brooklyn, New York (1937-1939). Among the principal artists Diller selected for this project were Jan Matulka, Stuart Davis, and Paul Kelpe, who were all permitted to execute their own designs." Other artists who had the support of Diller for projects as part of the Federal Art Project were Arshile Gorky, Ilya Bolotowsky, Jackson Pollock, and Willem de Kooning. Some of the major abstract murals supervised by Diller during this time include those at the Newark Airport by Gorky and the Williamsburg Housing Project by Bolotowsky. "With the entry of the United States into World War II, areas of the WPA were transferred to the War Service division, and from 1941 until 1943, Diller directed the New York City War Service Art Project."