An electronic screen capable of showing dynamic images is used to display a set of barcodes, where the barcodes are ‘played’ at the same location on the screen. The screen might also show other material. The data encoded in the barcodes is decoded by a user with a cellphone and camera, that can decode each barcode and combine the data from all the barcodes. This can be extended with the screen also showing static barcodes that encode URLs, where the URLs go back to a web server that also controls the screen. A user with a cellphone and camera scans one of these static barcodes and uses a browser to go to the decoded URL. The web server uses this visit to change what is being shown in the dynamic barcodes, or to change the conditions under which the latter are displayed.