In the same spirit I would recommend that you try section 2.2.4[1] of the SICP textbook using The SICP Picture Language [2] which can be found here [3].

That section is based on the same original paper, and it is very nice to check on the book's explanation using a modern environment such as DrScheme.

[1] http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-15.html...

[2] http://planet.plt-scheme.org/package-source/soegaard/sicp.pl...

[3] http://planet.plt-scheme.org/display.ss?package=sicp.plt&...