This is a nifty little feature to drag people's attention towards something special. It has to be used with caution, though, then too much of such a pulsating feature may easily become an annoyance.
It is quickly made, but there are some details to be aware of to make editing easier. The container .tap-target-content contains the actual contents of that blob that appears when you click the Open button. In this case I have popped in a heading and a paragraph, and the text is supposed to be white. In order to see what you are doing, make it first an 'any old' container, anywhere on the canvas, and fill it with the contents you want to have there. Then is the time to position it inside the .tap-target container and give it the correct class names.
You can make a component of this by selecting the container .tap-wrapper.