diff --git a/lib/main.rb b/lib/main.rb
new file mode 100644
index 00000000..5b2c06bf
--- /dev/null
+++ b/lib/main.rb
@@ -0,0 +1,77 @@
+require_relative 'planet'
+require_relative 'solar_system'
+
+def main
+  solar_system = SolarSystem.new("Sun")
+  mercury = Planet.new("Mercury", "light-grey", 3.285e23, 5.800e7, "if you lived on Mercury you'd have a birthday every 3 months.")
+  venus = Planet.new("Venus", "white", 4.867e24, 1.080e8, "it is named after the Roman goddess of love and beauty.")
+  earth = Planet.new("Earth", "blue-green", 5.972e24, 1.496e8, "it is the only planet known to support life.")
+  mars = Planet.new("Mars", "red", 6.39e23, 2.066e8, "it has the highest mountain in our solar system (24km).")
+  jupiter = Planet.new("Jupiter", "yellow-orange", 1.898e27, 7.680e8, "it has 79 moons.")
+  saturn = Planet.new("Saturn", "yellow-brown", 5.68e26, 1.426e9, "one of Saturn's rings, discovered in 2009, could fit a billion earths.")
+  uranus = Planet.new("Uranus", "blue-green", 8.681e25, 2.959e9, "it was the first planet discovered by a telescope in 1781.")
+  neptune = Planet.new("Neptune", "blue", 1.024e26, 4.476e9, "a year on Neptune is equivalent to 165 years on Earth.")
+
+  solar_system.add_planet(mercury)
+  solar_system.add_planet(venus)
+  solar_system.add_planet(earth)
+  solar_system.add_planet(mars)
+  solar_system.add_planet(jupiter)
+  solar_system.add_planet(saturn)
+  solar_system.add_planet(uranus)
+  solar_system.add_planet(neptune)
+
+  list = solar_system.list_planets
+
+  puts "Welcome to the Solar System Program! You may: \n 1. Check out a list of the planets \n 2. Learn about a planet \n 3. Add a planet \n 4. Calculate the distance between two planets \n 5. Exit"
+
+  user_input = nil
+
+  until user_input == 5
+    puts
+    print "Please enter a number to continue: "
+    user_input = gets.chomp.to_i
+      until user_input >= 1 && user_input <= 5
+      print "Sorry, that is not a valid option. Please check the list and try again: "
+      user_input = gets.chomp.to_i
+      end
+
+    case user_input
+    when 1
+      puts list
+    when 2
+      puts "Which planet do you want details on?"
+      planet = gets.chomp
+      info = solar_system.find_planet_by_name(planet)
+      puts info.summary
+    when 3
+      puts "Add a planet by entering the following information."
+      print "Name: "
+      name = gets.chomp.capitalize
+      print "Color: "
+      color = gets.chomp.downcase
+      print "Mass (Kg): "
+      mass = gets.chomp.to_f
+      print "Distance From Sun (Km): "
+      distance = gets.chomp.to_f
+      print "Fun Fact: "
+      fact = gets.chomp.downcase
+      user_planet = Planet.new(name, color, mass, distance, fact)
+      solar_system.add_planet(user_planet)
+      puts "Your planet has been added to the solar system! Here is the updated list: "
+      list = solar_system.list_planets
+      print list
+    when 4
+      print "Enter the first planet: "
+      first_planet = gets.chomp.capitalize
+      print "Enter the second planet: "
+      second_planet = gets.chomp.capitalize
+      puts "The distance between #{first_planet} and #{second_planet} is #{solar_system.distance_between(first_planet, second_planet)} km."
+    when 5
+      puts "Thank you for using the Solar System Program. Goodbye!"
+      exit
+    end
+  end
+end
+
+main
diff --git a/lib/planet.rb b/lib/planet.rb
new file mode 100644
index 00000000..8f7db3ef
--- /dev/null
+++ b/lib/planet.rb
@@ -0,0 +1,23 @@
+class Planet
+  attr_reader :name, :color, :mass_kg, :distance_from_sun_km, :fun_fact
+
+  def initialize(name, color, mass_kg, distance_from_sun_km, fun_fact)
+    @name = name
+    @color = color
+    @mass_kg = mass_kg
+    @distance_from_sun_km = distance_from_sun_km
+    @fun_fact = fun_fact
+
+    if mass_kg <= 0
+      raise ArgumentError.new("Mass must be greater than 0 kg.")
+    end
+
+    if distance_from_sun_km <= 0
+      raise ArgumentError.new("Distance from the sun must be greater than 0 km.")
+    end
+  end
+
+  def summary
+    return "#{@name} is #{@color}, weighs #{@mass_kg} kg, and is #{@distance_from_sun_km} km from the sun. A fun fact is that #{@fun_fact}"
+  end
+end
\ No newline at end of file
diff --git a/lib/solar_system.rb b/lib/solar_system.rb
new file mode 100644
index 00000000..9a7449af
--- /dev/null
+++ b/lib/solar_system.rb
@@ -0,0 +1,37 @@
+require_relative 'planet'
+
+class SolarSystem
+  attr_reader :star_name, :planets
+
+  def initialize(star_name)
+    @star_name = star_name
+    @planets = []
+  end
+
+  def add_planet(planet)
+    @planets << planet
+  end
+
+  def list_planets
+    output_string = "Planets orbiting the #{@star_name} \n"
+    @planets.each_with_index do |planet, index|
+      output_string += "#{index + 1}. #{planet.name} \n"
+    end
+    return output_string
+  end
+
+  def find_planet_by_name(planet_name)
+    found_planet = @planets.find { |planet| planet.name == planet_name.capitalize}
+    if found_planet.nil?
+      raise ArgumentError.new("Sorry, that planet does not exist in this solar system.")
+    end
+    return found_planet
+  end
+
+  def distance_between(first_planet, second_planet)
+    first_planet_distance = find_planet_by_name(first_planet).distance_from_sun_km
+    second_planet_distance = find_planet_by_name(second_planet).distance_from_sun_km
+    distance_between_planets = (first_planet_distance - second_planet_distance).abs
+    return distance_between_planets
+  end
+end
\ No newline at end of file
diff --git a/main.rb b/main.rb
new file mode 100644
index 00000000..a34efe99
--- /dev/null
+++ b/main.rb
@@ -0,0 +1,69 @@
+require_relative 'planet'
+require_relative 'solar_system'
+
+def main
+  solar_system = SolarSystem.new("Sun")
+  mercury = Planet.new("Mercury", "light-grey", 3.285e23, 5.800e7, "if you lived on Mercury you'd have a birthday every 3 months.")
+  venus = Planet.new("Venus", "white", 4.867e24, 1.080e8, "it is named after the Roman goddess of love and beauty.")
+  earth = Planet.new("Earth", "blue-green", 5.972e24, 1.496e8, "it is the only planet known to support life.")
+  mars = Planet.new("Mars", "red", 6.39e23, 2.066e8, "it has the highest mountain in our solar system (24km).")
+  jupiter = Planet.new("Jupiter", "yellow-orange", 1.898e27, 7.680e8, "it has 79 moons.")
+  saturn = Planet.new("Saturn", "yellow-brown", 5.68e26, 1.426e9, "one of Saturn's rings, discovered in 2009, could fit a billion earths.")
+  uranus = Planet.new("Uranus", "blue-green", 8.681e25, 2.959e9, "it was the first planet discovered by a telescope in 1781.")
+  neptune = Planet.new("Neptune", "blue", 1.024e26, 4.476e9, "a year on Neptune is equivalent to 165 years on Earth.")
+
+  solar_system.add_planet(mercury)
+  solar_system.add_planet(venus)
+  solar_system.add_planet(earth)
+  solar_system.add_planet(mars)
+  solar_system.add_planet(jupiter)
+  solar_system.add_planet(saturn)
+  solar_system.add_planet(uranus)
+  solar_system.add_planet(neptune)
+
+  list = solar_system.list_planets
+
+  puts "Welcome to the Solar System Program! You may: \n 1. See a list of the planets \n 2. See details for a planet \n 3. Add a planet \n 4. Exit"
+
+  user_input = nil
+
+  until user_input == 4
+    puts
+    print "Please enter a number to continue: "
+    user_input = gets.chomp.to_i
+      until user_input >= 1 && user_input <= 4
+      print "Sorry, that is not a valid option. Please check the list and try again: "
+      user_input = gets.chomp.to_i
+      end
+
+    case user_input
+    when 1
+      puts list
+    when 2
+      puts "Which planet do you want details on?"
+      planet = gets.chomp
+      info = solar_system.find_planet_by_name(planet)
+      puts info.summary
+    when 3
+      puts "Add a planet by entering the following information."
+      print "Name: "
+      name = gets.chomp
+      print "Color: "
+      color = gets.chomp
+      print "Mass (Kg): "
+      mass = gets.chomp
+      print "Distance From Sun (Km): "
+      distance = gets.chomp
+      print "Fun Fact: "
+      fact = gets.chomp
+      user_planet = Planet.new(name, color, mass, distance, fact)
+      solar_system.add_planet(user_planet)
+      puts "Awesome! Your planet has been added to the solar system."
+    when 4
+      puts "Thank you for using the Solar System Program. Goodbye!"
+      exit
+    end
+  end
+end
+
+main
diff --git a/planet.rb b/planet.rb
new file mode 100644
index 00000000..16347822
--- /dev/null
+++ b/planet.rb
@@ -0,0 +1,15 @@
+class Planet
+  attr_reader :name, :color, :mass_kg, :distance_from_sun_km, :fun_fact
+
+  def initialize(name, color, mass_kg, distance_from_sun_km, fun_fact)
+    @name = name
+    @color = color
+    @mass_kg = mass_kg
+    @distance_from_sun_km = distance_from_sun_km
+    @fun_fact = fun_fact
+  end
+
+  def summary
+    return "#{@name} is #{@color}, weighs #{@mass_kg} kg, and is #{@distance_from_sun_km} km from the sun. A fun fact is that #{@fun_fact}"
+  end
+end
\ No newline at end of file
diff --git a/solar_system.rb b/solar_system.rb
new file mode 100644
index 00000000..141a278d
--- /dev/null
+++ b/solar_system.rb
@@ -0,0 +1,30 @@
+require_relative 'planet'
+
+class SolarSystem
+  attr_reader :star_name, :planets
+
+  def initialize(star_name)
+    @star_name = star_name
+    @planets = []
+  end
+
+  def add_planet(planet)
+    @planets << planet
+  end
+
+  def list_planets
+    output_string = "Planets orbiting the #{@star_name} \n"
+    @planets.each_with_index do |planet, index|
+      output_string += " #{index + 1}. #{planet.name} \n"
+    end
+    return output_string
+  end
+
+  def find_planet_by_name(planet_name)
+    found_planet = @planets.find { |planet| planet.name == planet_name.capitalize}
+    if found_planet.nil?
+      raise ArgumentError.new("Sorry, that planet does not exist in this solar system.")
+    end
+    return found_planet
+  end
+end
\ No newline at end of file
diff --git a/test/planet_test.rb b/test/planet_test.rb
new file mode 100644
index 00000000..188258d9
--- /dev/null
+++ b/test/planet_test.rb
@@ -0,0 +1,36 @@
+require 'minitest/autorun'
+require 'minitest/reporters'
+require 'minitest/skip_dsl'
+
+require_relative '../lib/planet.rb'
+
+Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
+
+describe 'Planet' do
+  it 'creates an instance of Planet' do
+    name = 'Earth'
+    color = 'blue-green'
+    mass_kg = 5.972e24
+    distance_from_star_km = 1.496e8
+    fun_fact = "it is the only planet known to support life."
+
+    earth = Planet.new(name, color, mass_kg, distance_from_star_km, fun_fact)
+    expect(earth).must_be_instance_of Planet
+  end
+
+  it 'raises an error when the mass or distance from the sun are less than or equal to 0' do
+    expect {Planet.new('Earth','blue-green',0,1.496e8 ,"it is the only planet known to support life.")}.must_raise ArgumentError
+    expect {Planet.new('Earth','blue-green',5.972e24,0,"it is the only planet known to support life.")}.must_raise ArgumentError
+  end
+
+  it 'returns a summary for an instance of Planet' do
+    name = 'Earth'
+    color = 'blue-green'
+    mass_kg = 5.972e24
+    distance_from_star_km = 1.496e8
+    fun_fact = "it is the only planet known to support life."
+
+    earth = Planet.new(name, color, mass_kg, distance_from_star_km, fun_fact)
+    expect(earth.summary).must_equal "Earth is blue-green, weighs 5.972e+24 kg, and is 149600000.0 km from the sun. A fun fact is that it is the only planet known to support life."
+  end
+end
diff --git a/test/solar_system_test.rb b/test/solar_system_test.rb
new file mode 100644
index 00000000..f21c87c7
--- /dev/null
+++ b/test/solar_system_test.rb
@@ -0,0 +1,79 @@
+require 'minitest/autorun'
+require 'minitest/reporters'
+require 'minitest/skip_dsl'
+
+require_relative '../lib/solar_system.rb'
+
+Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
+
+describe 'Solar System' do
+  describe 'initialize solar system' do
+    it 'creates an instance of Solar System' do
+      star_name = 'Sun'
+      solar_system = SolarSystem.new(star_name)
+      expect(solar_system).must_be_instance_of SolarSystem
+    end
+  end
+end
+
+  describe 'add planet' do
+    it 'adds a planet' do
+      solar_system = SolarSystem.new("Sun")
+
+      earth = Planet.new('Earth','blue-green',5.972e24,1.496e8,"it is the only planet known to support life.")
+      mars = Planet.new("Mars", "red", 6.39e23, 2.066e8, "it has the highest mountain in our solar system (24km).")
+
+      solar_system.add_planet(earth)
+      solar_system.add_planet(mars)
+
+      expect(solar_system.planets.length).must_equal 2
+    end
+  end
+
+  describe 'list planet' do
+    it 'lists the planets' do
+      solar_system = SolarSystem.new('Sun')
+      expect(solar_system.list_planets).must_be_instance_of String
+
+      earth = Planet.new('Earth','blue-green',5.972e24,1.496e8,"it is the only planet known to support life.")
+      mars = Planet.new("Mars", "red", 6.39e23, 2.066e8, "it has the highest mountain in our solar system (24km).")
+      solar_system.add_planet(earth)
+      solar_system.add_planet(mars)
+      expect(solar_system.list_planets).must_equal "Planets orbiting the Sun \n1. Earth \n2. Mars \n"
+    end
+  end
+
+  describe 'finds a planet by name' do
+    it 'raises an error if the planet cannot be found' do
+    solar_system = SolarSystem.new("Sun")
+
+    earth = Planet.new('Earth','blue-green',5.972e24,1.496e8,"it is the only planet known to support life.")
+    mars = Planet.new("Mars","red",6.39e23,2.066e8,"it has the highest mountain in our solar system (24km).")
+
+    solar_system.add_planet(earth)
+    solar_system.add_planet(mars)
+
+    expect{solar_system.find_planet_by_name("Mercury")}.must_raise ArgumentError
+    end
+
+    it 'if the planet can be found it must be an instance of the class Planet' do
+      solar_system = SolarSystem.new("Sun")
+      earth = Planet.new('Earth','blue-green',5.972e24,1.496e8,"it is the only planet known to support life.")
+      solar_system.add_planet(earth)
+      expect(solar_system.find_planet_by_name("Earth")).must_be_instance_of Planet
+    end
+  end
+
+  describe 'distance between' do
+    it 'calculates the distance between two planets' do
+    solar_system = SolarSystem.new("Sun")
+
+    earth = Planet.new("Earth",'blue-green',5.972e24,1.496e8,"it is the only planet known to support life.")
+    mars = Planet.new("Mars","red",6.39e23,2.066e8,"it has the highest mountain in our solar system (24km).")
+
+    solar_system.add_planet(earth)
+    solar_system.add_planet(mars)
+
+    expect(solar_system.distance_between("Earth", "Mars")).must_be_close_to 57000000
+    end
+  end