diff --git a/solar-system.rb b/solar-system.rb
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+# Define the class Solar System
+class SolarSystem
+  attr_reader :planets, :age, :planet_names
+
+  # Initialize @planets as an array of planet instances
+  def initialize(planets)
+    @planets = planets
+    @age = 4600 # in million of years
+    @planet_names = []
+  end
+
+  # Method to add planets to the array
+  def add_planet(planet_to_add)
+    @planets << planet_to_add
+  end
+
+  # Generates a list of planet names
+  def list_planets
+    planet_list = ''
+    i = 0
+    @planets.each do |planet|
+      i += 1
+      planet_list << "#{i}. #{planet.name.capitalize}\n"
+    end
+    planet_list
+  end
+
+  # This method finds the distance assuming they are in a straight line out from the sun.
+  def find_distance_between_planets(planet_1, planet_2)
+    information_hash = {}
+    information_hash[:planet_1] = @planets[planet_1.to_i].name
+    information_hash[:planet_2] = @planets[planet_2.to_i].name
+    distance = @planets[planet_1.to_i].distance_from_sun - @planets[planet_2.to_i].distance_from_sun
+    information_hash[:distance] = distance.abs
+
+    information_hash
+  end
+end # End of Solar System class
+
+class Planet
+  attr_reader :name, :diameter, :distance_from_sun, :year_length, :color
+
+  def initialize(attributes = {})
+    @name = attributes[:name]
+    @diameter = attributes[:diameter] # measured in km
+    @distance_from_sun = attributes[:distance_from_sun] # measured in million km
+    @year_length = attributes[:year_length] # measured in Earth years
+    @color = attributes[:color]
+  end
+
+  def return_attributes
+    planet_summary = "
+    Name: #{@name}
+    Diameter: #{@diameter}
+    Color: #{@color}
+    Length of Year (in Earth years): #{@year_length}
+    Distance from the sun: #{@distance_from_sun} million km"
+    planet_summary
+  end
+end # End of Planet class
+
+# Initial message used to let the determine how they want to interact with the program.
+def get_choice
+  puts "\nThank you for using our Solar System Explorer! Here are your options:
+  (A) Add a planet to the list
+  (B) View a planet
+  (C) Exit the program"
+  print "\nPlease select a letter: "
+  choice = gets.chomp.upcase
+  choice
+end
+
+# If the user enters a planet name the first time, it will be accepted. If the user does not enter a correct number or name it will prompt them to enter an existing number until they do.
+def valid_entry(solar_system)
+  print 'Select a planet: '
+  planet_number = gets.chomp
+
+  # If user does not enter a valid name or number they will be prompted to enter again.
+  until (planet_number.to_i.to_s == planet_number) && (planet_number.to_i <= solar_system.planets.length && planet_number.to_i > 0)
+    print 'Please select a valid number to represent a planet: '
+    planet_number = gets.chomp
+  end
+  planet_number = planet_number.to_i - 1
+  planet_number
+end
+
+# (Choice A)
+def create_new_planet
+  planet = {}
+  planet[:name] = ''
+  while planet[:name] == ''
+    puts 'Please enter the name of the planet you would like to add: '
+    planet[:name] = gets.chomp.capitalize
+  end
+  puts 'Please provide the following attributes.'
+  print 'Diameter(in km): '
+  planet[:diameter] = gets.chomp
+  print "Distance from the Sun (or it's star) (units: million km): "
+  planet[:distance_from_sun] = gets.chomp
+  print 'Length of Year (units: Earth years): '
+  planet[:year_length] = gets.chomp
+  print 'Color: '
+  planet[:color] = gets.chomp
+
+  planet_object = Planet.new(planet)
+  planet_object
+end
+
+# (Choice B)
+def view_planet_summary(solar_system)
+  puts "Choose a planet to view some of it's information: "
+  puts solar_system.list_planets
+  planet_chosen = valid_entry(solar_system)
+  puts solar_system.planets[planet_chosen].return_attributes
+end
+
+# (Choice C)
+
+def leave_program
+  puts 'Thank you! Have a nice day!'
+  exit
+end
+
+# Pre-populated solar system
+# distance from sun is represented in million km.
+planets_in_ss = [
+  {
+    name: 'Mercury',
+    diameter: 4_878,
+    color: 'gray',
+    year_length: 0.241,
+    distance_from_sun: 57.9
+  },
+  {
+    name: 'Venus',
+    diameter: 12_104,
+    color: 'yellow',
+    year_length: 0.615,
+    distance_from_sun: 108.2
+  },
+  {
+    name: 'Earth',
+    diameter: 12_760,
+    color: 'blue',
+    year_length: 1,
+    distance_from_sun: 149.6
+  },
+  {
+    name: 'Mars',
+    diameter: 6_787,
+    color: 'red',
+    year_length: 1.88,
+    distance_from_sun: 227.9
+  },
+  {
+    name: 'Jupiter',
+    diameter: 139_822,
+    color: 'orange and white',
+    year_length: 11.86,
+    distance_from_sun: 778.3
+  },
+  {
+    name: 'Saturn',
+    diameter: 120_500,
+    color: 'pale gold',
+    year_length: 29.46,
+    star_system: 'Solar',
+    distance_from_sun: 1427
+  }
+
+]
+
+# Creates an array of planet objects based on the planet hashes defined above.
+solar_system_planets = []
+planets_in_ss.each do |planet_hash|
+  solar_system_planets << Planet.new(planet_hash)
+end
+
+# Creates a new solar system instance based on the planet instances
+solar_system_object = SolarSystem.new(solar_system_planets)
+
+# User interface
+loop do
+  choice = get_choice
+  case choice
+  when 'A'
+    new_planet = create_new_planet
+    solar_system_object.add_planet(new_planet)
+  when 'B'
+    view_planet_summary(solar_system_object)
+  when 'C'
+    leave_program
+  else
+    puts "\nI'm sorry that's not a valid selection. Please try again."
+  end
+end