 This program starts out by defining a couple of colors. This one we're going to use is the background color right here. And this one we're going to use later on. Here's the set of block where we tell it what size we want to make the display window and we tell it to make the background a certain color. Down here in the draw block we're setting the stroke weight to 2. And then I have a little comment that explains about what's going to happen for the rest of the program. When you press is a boolean variable and that means it just has two states, true or false, offer on. And it's an intrinsic variable set by processing, but you can declare your own boolean variables. Sometimes they're useful if you want to test if it's offer on and then do a bunch of stuff in case it is, for example. So this is a statement test to see whether you're pressing a key and if that key happens to be the R key. And if all those things are true, then it's going to draw a red line on the display window like this. This is a statement test to see whether or not you're pressing down a key and if that key happens to be the K key. And if it is, then it will draw a black line on your screen. So this is what it looks like when it's running. Now here's kind of the limitation of what a screencast can do for you. Right now you just have to trust me that I'm not holding down any keys. Now I'm going to hit the R key and when I wiggle my mouse around I make a line. I let my finger off the R key so now I'm not doing anything anymore. I'm going to hit the K key and you can see it draws a black line.