As a rule of thumb/advice: usage of `@@variable_name` is heavily discouraged. They're called class variables and their lookup is very weird. They are accessible in the class and its instances... and maybe the parent and child classes as well? Hell I don't even know anymore.

What is encouraged on the other side are class instance variables. E.g. instance variables on the class object (as in Ruby everything is an object!).

E.g.

```ruby
class MyClass
  @class_instance_variable = :foo

  def bla
    @normal_instance_vairable = bar
  end

  def self.foo
    @class_instance_variable #accessible from methods defined on the class itself
  end

  def get_me_foo
    self.class.foo # you can access it like this from an instance
  end

end