Rubinius is a Ruby implementation known for being "written in Ruby", although that's not entirely true since it does have a large VM written in C++. We'll start off by briefly looking at the structure of Rubinius, focusing on the load order and object system bootstrapping. Then we'll remove a feature from it by updating all of the source files that reference that feature, then verifying the change both by running the tests and by visual inspection.
Note: At the very beginning, I misspeak and say that Class's superclass is Class. This isn't true: Class's superclass is Module, and the class of Class is Class, which is what's being set up in the line in question. Object system bootstrapping is hard to keep straight!