 There's a couple of new things in this program. One is the addition of this variable, which is shorthand for x direction. And we're giving it the value of 1 to start with. So when we increment x, we're saying x equals x plus 1. So that's not really changing anything that we had before. But now down here, we're going to have an if test. And we're going to say if x becomes greater than the width of the window, then we are going to multiply x direction by negative 1, so that it becomes a negative number. Then the next time processing loops through a draw, x will be going the other direction because this is negative 1 instead of positive 1. So that looks like this. And what we're hoping is that the lightning bolt is going to turn around when it gets here. And it does. That's good. That is what we wanted. But now we have a problem, which is it runs off the left side of the picture, never to return. So what we really want to do is not just say that if x equals the width of the window to turn around, we want it to say if x equals the width of the window, or if it comes back and equals 0, we want to turn around again. So the way to do that is to add something into this if test. We want to tell it if x becomes greater than the width of the window, or x becomes less than 0 to multiply the direction by negative 1. So that way you can see what's going to happen. If it gets to the edge of the window on the right side, x star becomes negative 1. Then when it gets back to 0, we'll multiply this by negative 1. Again, it'll become positive 1. It'll go back the other way. This thing that I typed here means or, and it's accomplished by typing two pipes, two vertical lines. And where you find that on your keyboard is normally on the same key as the backspace key, at least on a Mac keyboard, between delete and return. So look for that. Let's watch this one run. That's good. That's what we wanted. And this will just keep going infinitely back and forth until we tell it to stop. I actually think it would be more aesthetically pleasing if the lightning bolt on the right side didn't run all the way off the page before it came back. And we can do that by making it bounce back at a different place. So specifically, the widest this lightning bolt ever is, I think, is x plus 40. That occurs in two places. So why don't we tell it to turn around when it gets to the value of width minus 40? I bet that'll look better. Let's try that. Oh, good. That's what I wanted. And this will keep going over and over again until we tell it to stop by shutting it down here.