If you look at his script the blocking system lets you hide html elements with css, too hide the app store banner all you have to do is inspect element in chrome, find the element id/class and set it to display none.
i used a for loop to print out the div's with a random color and increment left: by 0.5 at a time.
It also lets me enter in the increment value via a html form.
Im pretty new to coding and you both seem knowledgeable, how would you go about to make the same effect in a web browser