I would search for "Squeak By Example" and read through the book. It is Smalltalk, aka the seminal OO language. It also provides all of the code use to create

I would search for "Squeak By Example" and read through the book. It is Smalltalk, aka the seminal OO language. It also provides all of the code use to create the system and the VM it runs on in a readable, editable, runnable format so you can play with everything. Reading the code was really eye opening for me. And super fun to boot!