 So up here at the top of the program, we are going to set two color variables and call them value and value 2. In the setup block, we set the size of the display window and we set the background to white. Inside the draw block, all we do is set the first fill value that we already specified up here and draw square. And then we set another fill value that we specified up here and draw another square. That's all this will do. But in case we click the mouse inside the display window, that triggers this function to run. And this function has a kind of a complicated if statement series nestled inside it. So let's just run the program and I can go through what this does. So the default is to plot these two squares with these colors. Now if I click the mouse inside the display window, this first if statement test to see whether the cursor is inside the top square. And if it is, it changes the color of the bottom square. That's actually what both of these two statements take care of. So if I click in here, I'm toggling the color of the bottom square. The next two statements test whether the cursor has been clicked inside the bottom square. And if it has, then it changes the color of the top square. So clicking in here toggles the color of the top square. But what if I click them as somewhere other place in the display window? It's not in either of these two squares. Then the string that I wrote tells me that I did something unexpected. So what these series of statements do is this test to see whether this is true. And if it is, it does this command and ignores everything else. But if it's not true, it sees this else of statement and it looks to see if this one is true. And if it is, it executes this command and ignores everything else. And that keeps going along. If it turns out that none of these are true, by default it executes this command. So writing an else statement at the bottom of a series of ifs and elseifs is kind of a good failsafe procedure because it can alert you that something has happened inside your function that you didn't cover with all your other possibilities.