This step-by-step script building demonstration (with highlighted "new" lines!) is just awesome. I've seen this approach in a couple of programming books, but hardly ever on programming blogs.
This is particularly helpful for developers like me who jump daily between many different languages. It helps me get the design down first and come back and worry about getting into a specific language syntax/mindset only after I've thought through all of the logic and conditions at a high-to-mid level.