An element of mobile interfaces, that appears behind all the app layers, showing interactional content that suits the context.
Backdrop consists of two layers, the front and the back one, and only one of them can be active at a time. The front layer displays the main information in the form of text, images, or cards. The back layer contains navigation, filters, selection controls, etc., and affects what is shown onto the front layer. A tap on the back layer activates it, turning the front layer into the scrim.