Hungarian-born painter, sculptor, and designer who settled in Paris in 1930 and became a French citizen in 1959, the main originator and one of the leading practitioners of *Op art. He studied in Budapest at the Poldini-Volkman Academy of Painting and the Mühely School (known as the *Bauhaus of Budapest) before he settled in Paris in 1930. For the next decade he worked mainly as a commercial artist, particularly on the designing of posters, showing a keen interest in visual tricks and space illusions. From 1943 he turned to painting and he had his first one-man exhibition in 1944, at Denise *René's gallery. About three years later he adopted the method of geometrical abstraction for which he is best known. Typically he created a hallucinatory impression of movement through visual ambiguity, using alternating positive–negative shapes in such a way as to suggest underlying secondary shapes.