A two dimensional barcode with default background and foreground colors uses other foreground colors, to make separate means of encoding data, used by decoding hardware and software, or by an observer's perception. The new colors show text or graphics. A barcode on a dynamic display shows a progress indicator for an operation started by a user who imaged the barcode with her phone. Or it shows the number of votes for users who picked it with their phones. The barcode could show scrolling text. A barcode on a computer screen simulates a pushbutton; pressed when the user takes a photo of it with a cellphone. Suppose a barcode has a symbol drawn on its foreground rectangles, and the barcode encodes a URL. The URL is crafted to maximize the number of foreground rectangles that the symbol intersects, helping a human interpolate the symbol from fragments.