Video is a one-way form of communication, so user's don't have the chance to ask you to clarify or ask "Where does X fit in?" This places the burden on you to guide their eyes as you explain how all the little pieces of the code fit together. When your application has a "flow", "X triggers Y, Y triggers Z", make sure to "show the flow" by walking them through where each chunk of code fits. This involves a lot of mouse movement (or fancy keyboard selection shortcuts) and hightlighting to bring it all together.
[00:00] Guide the users' eyes to help them follow along. For example, let's click on this button to show how this scan operator will handle incrementing each time the mouse is clicked.
[00:13] When I click over here, you can see this number increases because I'm adding one to the current total. You'll notice I did not write any code there. I was simply walking through the flow of the application.
[00:28] Anything I was interacting with, like the button or the scan operator I would highlight to draw their attention to that. This helps to keep you and the user on the exact same page.
[00:40] Also, if you need to say something like, "This is possible because in the Main.js file we registered Viewrx with you. And now, in our app file, we can use subscriptions."
[00:55] Anytime you reference something across your project, change the file, highlight what you're talking about. Be very explicit about where you're going and what you want them to look at, to really help them understand how all the little pieces fit together.