1. A computer-implemented method comprising: accessing first and second images of an object, the first image being captured while the object is illuminated with projected electromagnetic radiation, and the second image being captured while the projected electromagnetic radiation is extinguished; projecting at least a portion of the projected electromagnetic radiation as a first light curtain along and parallel to at least a portion of a first side of a screen; determining a position of the object relative to the screen based on comparing the first and second images; and controlling an application based on the determined position.