I LOVE this lesson! So much!
I taught this using a "code-along" style of the lesson - I looked at the little narration and did a think-out-loud with students that roughly followed that narrative. It was a great way to engage students a bit more evenly and hear how programming really happens - you throw out ideas, then throw out better ideas, you move code around, and test code repeatedly.
As we talked about the plan, I put in comments into my code on the screen to A) model making comments in code, and B) to allow students to "fill in" the code in the comments if they were able to independently.
I am wondering if people have other ideas for similar types of lessons/apps. Now that we have done this together, I would love to give students another mini-challenge to create given the design in place and have them create the algorithms/functions to get the app to work. Any suggestions?