Squeak is written in 230,000 lines of Smalltalk. They think it could be 20,000. There are 59,000 methods in 3.5Mb of object code, for about 59 bytes per method. There are about 5 million objects and it was implemented by ten people. The system is self-bootstrapping, so it’s all in there. Learning how to do this ought to be part of computer science but regrettably it’s not.