Responsive page using CSS flex-box

I think a way to implement the "mark as read" part it's maybe to put a button on that text and create a class with de read format (i think the main difference is the background-color, i didn't do this challenge yet) and with a little bit of JS set an eventlistener to that button with a toggle or and add to establish the class with the read format on the elements (previusly you must create variables to each element that you would like to transform). You can do it only with JS or use some Jquery. Hope this works! Good luck!