1. A system comprising: one or more processors; and memory having one or more instructions stored thereon that, responsive to execution by the one or more processors, perform operations comprising: presenting, in a visible region of an application-selectable user interface, a set of tiles associated with a set of applications; determining a subset of the set of tiles associated with a subset of applications for which new content is available, at least one tile of the subset of the set of tiles for which new content is available being associated with an application of the subset of applications that is not executing and for which new content or an indication thereof has been received from an entity other than the application that is not executing; determining that a number of tiles of the subset associated with the subset of applications for which new content is available or a fraction of the subset associated with the subset of applications for which new content is available relative to the set of tiles associated with the set of applications exceeds a pre-determined threshold, the pre-determined threshold based on a mental or visual overload or over-stimulation limit; and responsive to determining that the number of tiles of the subset or the fraction of the subset exceeds the pre-determined threshold, progressively indicating, from one side or corner of the visible region to an opposite side or opposite corner of the visible region, in each of the tiles of the subset that new content is available.