1. A computer-implemented method comprising: accessing first and second images, captured on a first side of a screen, of an object and an ambient electromagnetic radiation emitter disposed on a second side of the screen, 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; 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.