I've got environments mostly done. There are some loose ends related to the fact that my on-the-fly redesign (of course I have an on-the-fly redesign) in some sense "wants" garbage collection, and is somewhat set up to support it, but does not currently have it. Currently, namespaces just always exist, and all the changes is the index into an arena. Ideally, there should be some kind of ref-counting happening, but I think it would be prudent to wait to get to closures before messing with that.
Along with environments, I've got support for most kinds of statement currently in the grammar, and I also fixed up the support for some of the stuff that I added in response to the challenges.
I also also made some improvements to testing coverage. There'll be some un-fixable shortcomings until I get through the next few chapters, but the coverage is still much better. Anyway, it's late and hot.