The course is based on the general principles which underlay HtDP. But HtDP is Matthies Felliesen's particular approach, and Gregor Kiczales (CLOS, Aspect Oriented Programming, The Meta-Object Protocol) has his own points of emphasis.

What both share is a general approach to programming pedagogy - that of the larger Racket community. It includes starting with a simple functional language, BSL, in order to avoid getting hung up on language syntax and to provide better error messages during debugging. BSL prevents FORTRAN in any languages, everything has to be functional. Because it only has

  cons

But not

   list

BSL programs tend to make structure explicit - don't worry, list is added when appropriate.

At first this seems like a lot more training wheels than necessary, but it allows the course to focus on writing signatures, descriptions, and templates in the first weeks, and pays off handsomely when the material hits recursion - there were very few questions about it in the forums, and the answer when those who couldn't picture it felt stuck was, for now just trust the template.

The big idea of the course is to teach a design method. It does so by looking at recursive algorithms and presenting recipes for applying them. The second theme is functional style programming - and it is dictated by necessity. The third theme is model-view-controller through Racket's "worlds".

I've taken a lot away from it, your milage may vary.