class Citizen
  attr_reader :first_name

  # DATA (instance variables)
  def initialize(first_name, last_name, age) # also called constructor in English
    @first_name = first_name # instance variable
    @last_name = last_name # instance variable
    @age = age # instance variable
  end

  # BEHAVIOR (instance methods)
  def can_vote?
    return @age >= 18
  end

  def full_name
    return "#{@first_name.capitalize} #{@last_name.capitalize}"
  end
end