Despite its humble size, this is a pretty sophisticated Lisp implementation. Not that one that can only do some additions, but also macros and stuff.

Kudos for doing the Lisp thing right.

UPDATE: Took one more look, this implementation is really impressive. It does stuff like 'defmacro', the whole code is just 1400 lines of C#. Never saw anything that effective in terms of functionality per line of code till this day. Impressive, very impressive. Also thanks for sharing.