Great idea. One small comment: Some of the text needs some work, e.g. for the free lesson on prototype two of the required materials are listed as "A4 paper" (would a letter-sized paper not do, is the specific size important? Better say "a sheet of paper that's larger than ...") and "some pencils" (some sounds strange here because pencil is a count noun).
Other than those, when I clicked on the next arrow on the first screen I was presented with a screen with problems (Chrome 38.0 on Mavericks): the text "2/20" was sitting on top of the instruction text and the window displayed nothing. Why not detect the user device and put a help message indicating that the site has to be used on a mobile device? When you say "You'll only need an iOS or Android device" in the course description I thought (mistakenly) that these will be required in addition to my laptop.