The card is data and four variables: name ('{name}'), age (a number in an expression and in a string), top and bottom (the two colours of the sky). Typing calls movie.setVars(). The batch button does what a shell script would: for each name it calls setVars and then movie.render({ format: 'mp4' }) and saves the file. From the command line: pixi-effects render card.html --var name=Aiko --var age=30 -o aiko.mp4.