GUIs were constructed solely from Actors. A window-like object could be built out of an opaque rectangle containing other objects (e.g., close buttons, widgets). Every Actor's drawing style was controlled by a Renderer, which aided the GUI building process. For instance, the BevelRenderer could be used to bevel the edges around an Actor, producing an effect like Windows 3.x controls or the title bar in NeXTSTEP. Other renderers included color and image fills, gradients, tiles and blends. Although there was no difference in programming terms, basic objects like rectangles were classified as "geometry actors" while more traditional GUI elements like buttons were known as "interface actors".