I set my Windows computer up with a great big huge magenta on-screen pointer. Just for fun, and because it's easy to see. A little fruit fly just started hiking up my screen. If I put the pointer under him, he stops. If I move the pointer away, he continues up the screen. I tried it 3 or 4 times, it worked every time. Then I let him get on about his business. I wonder if he thought "what the heck was that all about?"