diff --git a/.gitignore b/.gitignore
new file mode 100644
index 00000000..36298d28
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+.byebug_history
diff --git a/Rakefile b/Rakefile
new file mode 100644
index 00000000..0c2d13fe
--- /dev/null
+++ b/Rakefile
@@ -0,0 +1,9 @@
+require 'rake/testtask'
+
+Rake::TestTask.new do |t|
+  t.libs = ["lib"]
+  t.warning = true
+  t.test_files = FileList['test/*_test.rb']
+end
+
+task default: :test
diff --git a/lib/main.rb b/lib/main.rb
new file mode 100644
index 00000000..0d9bda2d
--- /dev/null
+++ b/lib/main.rb
@@ -0,0 +1,71 @@
+require 'byebug'
+require_relative 'planet'
+require_relative 'solar_system'
+
+def main
+  earth = Planet.new(
+      'Earth',
+      'blue-green',
+      5.972e+24,
+      149.6e+6,
+      "Only planet known to support life"
+  )
+
+  moon = Planet.new(
+      'Moon',
+      'grey',
+      7.348e+22,
+      150e+6,
+      "Earth's only natural satellite"
+  )
+
+  ##############################################
+
+  solar_system = SolarSystem.new('Sun')
+
+  solar_system.add_planet(earth)
+  solar_system.add_planet(moon)
+
+  ##############################################
+
+  continue = true
+  while continue
+    puts "This program has created a solar system with several planets. From here, you can:\n"
+    puts "1. List the planets in the solar system (enter 1)\n"
+    puts "2. Display details about a single planet in the system (enter 2)\n"
+    puts "3. Add a planet to the system (enter 3)\n"
+    puts "4. Calculate the distance between two planets (in km) (enter 4)\n"
+    puts "5. Exit (enter 5)\n"
+
+    response = gets.chomp.to_i
+
+    case response
+    when 1
+      puts solar_system.list_planets
+    when 2
+      puts "Please enter the name of the planet you'd like to know more about:"
+      planet_inspect = gets.chomp
+      planet_inspect = solar_system.find_planet_by_name(planet_inspect)
+      puts planet_inspect.summary
+    when 3
+      solar_system.user_add_planet
+    when 4
+      puts "Please enter the name of the first planet:"
+      planet_1 = gets.chomp
+      puts "Please enter the name of the second planet:"
+      planet_2 = gets.chomp
+
+      solar_system.find_planet_by_name(planet_1)
+      solar_system.find_planet_by_name(planet_2)
+      distance = solar_system.distance_between(planet_1, planet_2)
+      puts "The distance between #{planet_1} and #{planet_2} is approximately: #{distance} km."
+    when 5
+      puts "OK! Terminating program."
+      continue = false
+    else
+      puts "That was not a valid response."
+    end
+  end
+end
+
+main
\ No newline at end of file
diff --git a/lib/planet.rb b/lib/planet.rb
new file mode 100644
index 00000000..ebba3c47
--- /dev/null
+++ b/lib/planet.rb
@@ -0,0 +1,32 @@
+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
+
+    if (mass_kg.class == Float || mass_kg.class == Integer) && mass_kg > 0
+      @mass_kg = mass_kg
+    else
+      raise ArgumentError, "For #{self.name}, this isn't the right type of input for mass in kg - please enter an number greater than 0."
+    end
+
+    if (distance_from_sun_km.class == Float || distance_from_sun_km.class == Integer) && distance_from_sun_km > 0
+      @distance_from_sun_km = distance_from_sun_km
+    else
+      raise ArgumentError, "For #{self.name}, this isn't the right type of input for distance from sun in km - please enter an number greater than 0."
+    end
+
+    @fun_fact = fun_fact
+  end
+
+  def summary
+    stats = "<< Summary of planet: #{name.upcase} >>\n" +
+        "Color: #{color}\n" +
+        "Mass (kg): #{mass_kg}\n" +
+        "Distance from sun (km): #{distance_from_sun_km}\n" +
+        "Fun fact: #{fun_fact}"
+    return stats
+  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..0c27da3e
--- /dev/null
+++ b/lib/solar_system.rb
@@ -0,0 +1,64 @@
+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
+    summary_list = "Planets orbiting <#{@star_name}>\n"
+    @planets.each.with_index(1) { |planet, idx| summary_list << "#{idx}. #{planet.name}\n"}
+    return summary_list
+  end
+
+  def check_valid_planet(planet)
+    @planets.each do |one_planet|
+      if one_planet.name.upcase == planet.upcase
+        return one_planet
+      end
+    end
+    raise ArgumentError, "#{planet} is not part of the given solar system."
+  end
+
+  def find_planet_by_name(planet)
+    found_planet = check_valid_planet(planet)
+    return found_planet
+  end
+
+  def distance_between(planet_1, planet_2)
+    planet_1 = check_valid_planet(planet_1)
+    planet_2 = check_valid_planet(planet_2)
+    distance_bw_planets = (planet_1.distance_from_sun_km - planet_2.distance_from_sun_km).abs
+    return distance_bw_planets
+  end
+
+  def user_add_planet
+    puts "We need the following details about the planet:"
+    puts "What is the name of the planet?"
+    planet_name = gets.chomp
+    puts "What color is the planet?"
+    planet_color = gets.chomp
+    puts "What is the mass (in kg) of the planet?"
+    planet_mass_kg = gets.chomp.to_i
+    puts "What is the planet's distance from the sun (in km)?"
+    planet_dist_km = gets.chomp.to_i
+    puts "What is a fun fact about the planet?"
+    planet_fun_fact = gets.chomp
+
+    new_planet = Planet.new(
+        planet_name,
+        planet_color,
+        planet_mass_kg,
+        planet_dist_km,
+        planet_fun_fact
+    )
+
+    add_planet(new_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..6743196f
--- /dev/null
+++ b/test/planet_test.rb
@@ -0,0 +1,75 @@
+require 'minitest/autorun'
+require 'minitest/spec'
+require 'minitest/reporters'
+require 'minitest/pride'
+
+require_relative '../lib/planet'
+
+Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
+
+describe 'Correct initialize' do
+
+  it 'raises an ArgumentError for invalid measurement inputs' do
+    expect {
+      Planet.new(
+          'Earth',
+          'blue-green',
+          'very big',
+          149.6e+6,
+          "Only planet known to support life"
+      )
+    }.must_raise ArgumentError
+
+    expect {
+      Planet.new(
+          'Earth',
+          'blue-green',
+          5.972e+24,
+          'very far',
+          "Only planet known to support life"
+      )
+    }.must_raise ArgumentError
+
+    expect {
+      Planet.new(
+          'Earth',
+          'blue-green',
+          '',
+          'very far',
+          "Only planet known to support life"
+      )
+    }.must_raise ArgumentError
+  end
+
+  it 'raises an ArgumentError for measurement inputs <= 0' do
+    expect {
+      Planet.new(
+          'Earth',
+          'blue-green',
+          5.972e+24,
+          -149.6e+6,
+          "Only planet known to support life"
+      )
+    }.must_raise ArgumentError
+
+    expect {
+      Planet.new(
+          'Earth',
+          'blue-green',
+          -5.972e+24,
+          'very far',
+          "Only planet known to support life"
+      )
+    }.must_raise ArgumentError
+
+    expect {
+      Planet.new(
+          'Earth',
+          'blue-green',
+          0,
+          900,
+          "Only planet known to support life"
+      )
+    }.must_raise ArgumentError
+  end
+end
\ No newline at end of file
diff --git a/test/solar_system_test.rb b/test/solar_system_test.rb
new file mode 100644
index 00000000..df65cb4f
--- /dev/null
+++ b/test/solar_system_test.rb
@@ -0,0 +1,44 @@
+require 'minitest/autorun'
+require 'minitest/spec'
+require 'minitest/reporters'
+require 'minitest/pride'
+
+require_relative '../lib/planet'
+require_relative '../lib/solar_system'
+
+Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
+
+describe 'checking solar system planets' do
+  # Arrange
+  earth = Planet.new(
+      'Earth',
+      'blue-green',
+      5.972e+24,
+      149.6e+6,
+      "Only planet known to support life"
+  )
+
+  moon = Planet.new(
+      'Moon',
+      'grey',
+      7.348e+22,
+      150e+6,
+      "Earth's only natural satellite"
+  )
+  solar_system = SolarSystem.new('Sun')
+
+  solar_system.add_planet(earth)
+  solar_system.add_planet(moon)
+
+  it 'raises an ArgumentError for invalid planets in solar system' do
+    expect {
+      solar_system.check_valid_planet('not a real planet')
+    }.must_raise ArgumentError
+  end
+
+  it 'raises an ArgumentError for invalid planets in solar system' do
+    expect {
+      solar_system.check_valid_planet('')
+    }.must_raise ArgumentError
+  end
+end
\ No newline at end of file