1. Move your cursor onto the project. 2. While holding the mouse down, move it off the project to one of the surrounding buttons. 3. The variable will tell you what the mouse is touching.
While the mouse is held down, a project can track its location outside the project (sorta). This little project will tell you what it is. Oh, a note for whoever looks inside: the y min and max are flipped because I goofed up. Ooh, it looks like the top few buttons work without the mouse being down! :D