The window area is divided into several overlapping layers. The principal layer is the layer of items, which is denoted by the height level 0. In this layer the items of the main sheet are displayed. The main sheet is a picture grid of 32 x 32 graphical dots (pixels). Above the item layer sprites having a positive height level can be moved. Below the item layer sprites having a negative height level can be moved. The lowest layer is the graphic layer. Into this layer the dot graphics including pictures are displayed. In order that the graphic layer and sprites having a negative height level may be visible, it is necessary to make the items transparent by means of a transparent color (the first color at the upper left of the graphic editor).