method_names and variable_names are lower case, with underlines
filenames are lower case with underlines, named after the top_level_class.rb
Classes should be less than 100 lines long
Methods should be less than 15 lines long
No standalone code or definitions. Everything should be part of a class
No global variables
Instance variables are always private
Don’t use @@foo
instead of a method called “display” on a class, add a method called to_s which returns the class state as a text string. That way you can do a puts on it.