(b Zurich, 13 Sept. 1902; d Zurich, 16 Sept. 1988). Swiss painter and printmaker. In his early works he experimented with various subjects and styles, but in the 1940s he became one of the leading representatives of Concrete art. His paintings are mathematically based, often featuring chequerboard or grid-like patterns, but they are not cold or analytical in effect; indeed his work is particularly noted for its beauty and refinement of colour, and has a certain resemblance to Op art of the kind associated with Bridget Riley. From about 1950 he gained an international reputation.