At the beginning of the 13th century, plate tracery was superseded by bar-tracery. Bar-tracery divides the large lights from one another with moulded mullions. Stone bar-tracery, an important decorative element of Gothic styles, first was used at Reims Cathedral shortly after 1211, in the chevet built by Jean D'Orbais. It was employed in England around 1240. After 1220, master builders in England had begun to treat the window openings as a series of openings divided by thin stone bars, while before 1230 the apse chapels of Reims Cathedral were decorated with bar-tracery with cusped circles (with bars radiating from the centre). Bar-tracery became common after c.1240, with increasing complexity and decreasing weight. The lines of the mullions continued beyond the tops of the window lights and subdivided the open spandrels above the lights into a variety of decorative shapes. "Rayonnant" style (c.1230–c.1350) was enabled by the development of bar-tracery in Continental Europe and is named for the radiation of lights around a central point in circular rose windows. "Rayonnant" also deployed mouldings of two different types in tracery, where earlier styles had used moulding of a single size, with different sizes of mullions. The rose windows of Notre-Dame de Paris (c.1270) are typical.