car.rb

class Car # => UpperCamelCase
  # attr_reader :color, :brand
  # attr_writer :color
  attr_accessor :color, :brand

  def initialize(color, brand) # => constructor stores the data/state
    @color = color
    @brand = brand
    @engine_started = false # => instance variable
  end

  # => behavior
  # def color
  #   return @color    
  # end

  # def color=(color)
  #   @color = color
  # end

  def engine_started?
    @engine_started
  end

  def start_engine 
    start_fuel_pump
    init_spark_plug
    @engine_started = true
  end

  private # => Can't be called on an instance

  def start_fuel_pump
    # => Complex procedure
  end

  def init_spark_plug
  end

end

blue_car = Car.new("blue", "Volvo")
p blue_car.color
blue_car.color = "green"
p blue_car.color