This command creates a "plain vanilla" button that is transparent, and does absolutely nothing.
It is nonetheless surprisingly useful. You can use a Vanilla button as the starting point for a single chain, when you want to be able to click in one place and have a chain begin, in effect, somewhere else. For example you might want to be able to click in the lower right corner and have that click send you to another card. You could then put a vanilla button in the corner and chain it to the Link button, where you can then specify which card the lecture should move to. Or you might chain an invisible vanilla button at the lower right to a hiliter button at the upper left. Then you could hilite something in the upper left by clicking in the lower right.
Another use of vanilla buttons is discussed in the section on Inverter buttons.
