1. A non-transitory computer-readable storage medium encoded with executable instructions that, when executed by a processor, cause the processor to perform operations comprising: detecting, using electromagnetic radiation projected proximally to a surface, an object near the surface; determining whether the detected object is of a predetermined object type using a trained recognition model, the recognition model being trained to determine whether the detected object is of the predetermined object type based on an appearance of the detected object; and generating a user input to a computer application based on the detected object, if it is determined that the detected object is of the predetermined object type.