diff --git a/Gemfile b/Gemfile
new file mode 100644
index 00000000..2bd750b6
--- /dev/null
+++ b/Gemfile
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+source "https://rubygems.org"
+
+gem 'rake'
+gem 'minitest'
+gem 'minitest-spec'
+gem 'minitest-reporters'
+gem "pry"
+gem 'minitest-skip'
\ No newline at end of file
diff --git a/Gemfile.lock b/Gemfile.lock
new file mode 100644
index 00000000..630ea95b
--- /dev/null
+++ b/Gemfile.lock
@@ -0,0 +1,36 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    ansi (1.5.0)
+    builder (3.2.4)
+    coderay (1.1.3)
+    method_source (1.0.0)
+    minitest (5.14.2)
+    minitest-reporters (1.4.2)
+      ansi
+      builder
+      minitest (>= 5.0)
+      ruby-progressbar
+    minitest-skip (0.0.3)
+      minitest (~> 5.0)
+    minitest-spec (0.0.2.1)
+      minitest (>= 3.0)
+    pry (0.13.1)
+      coderay (~> 1.1)
+      method_source (~> 1.0)
+    rake (13.0.1)
+    ruby-progressbar (1.10.1)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  minitest
+  minitest-reporters
+  minitest-skip
+  minitest-spec
+  pry
+  rake
+
+BUNDLED WITH
+   2.1.4
diff --git a/Rakefile b/Rakefile
new file mode 100644
index 00000000..fb007c61
--- /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
\ No newline at end of file
diff --git a/lib/main.rb b/lib/main.rb
new file mode 100644
index 00000000..14cfac3c
--- /dev/null
+++ b/lib/main.rb
@@ -0,0 +1,140 @@
+# Pauline Chane (@PaulineChane)
+# Ada Developers Academy C14
+# Solar System Assignment - main.rb Main Class Driver/CLI methods
+# 09/23/2020
+
+# main.rb
+require_relative 'planet'
+require_relative 'solar_system'
+
+# defs for control loop actions that take a little more time
+# get detail for planet and account for invalid input
+def get_planet_detail(solar_system_obj)
+  print "Enter name of Planet: "
+  input = gets.chomp
+
+  # don't exit until name of findable planet is entered
+  while solar_system_obj.find_planet_by_name(input).nil? do
+    print "Planet not found in Solar System. Please try again: "
+    input = gets.chomp
+  end
+
+  return solar_system_obj.find_planet_by_name(input)
+end
+
+# get and validate user input for adding planet with new info
+def user_add_planet(solar_system_obj)
+  # prompt/input for all input parameters stored in individual variables
+  print "Enter planet name: "
+  name = gets.chomp
+
+  print "Enter planet color: "
+  color = gets.chomp
+
+  # mass must be greater than 0
+  print "Enter planet mass (in kg): "
+  mass = gets.chomp.to_f
+
+  while mass <= 0 do
+    puts "Invalid mass (in kg) input - must be greater than zero"
+    print "Enter planet mass (in kg): "
+    mass = gets.chomp.to_f
+  end
+
+  # distance from sun must be greater than zero
+  print "Enter planet's distance from the sun (in km): "
+  distance_from_sun = gets.chomp.to_f
+
+  while distance_from_sun <= 0 do
+    puts "Invalid distance from sun (in km) input - must be greater than zero"
+    print "Enter planet's distance from the sun (in km): "
+    distance_from_sun = gets.chomp.to_f
+  end
+
+  print "Enter planet fun fact: "
+  fun_fact = gets.chomp
+
+  new_planet = Planet.new(name, color, mass, distance_from_sun, fun_fact)
+
+  solar_system_obj.add_planet(new_planet)
+  return true
+end
+
+# get user input for two planets CURRENTLY in the solar system and return the distance between them
+# returns a 3 element array that allows for printing a string stating the distance between two planets.
+def user_input_distance(solar_system_obj)
+  puts "ENTER FIRST PLANET"
+  planet1 = get_planet_detail(solar_system_obj)
+
+  puts "ENTER SECOND PLANET"
+  planet2 = get_planet_detail(solar_system_obj)
+
+  return [planet1.name, planet2.name, solar_system_obj.distance_between(planet1.name, planet2.name)] # name of planets and distance between them
+end
+
+
+# code for driver itself
+def main
+  # create base solar_system with some planets
+  solar_system = SolarSystem.new('Sol')
+
+  earth = Planet.new('Earth', 'blue-green', 5.972e24, 1.496e8, 'Only planet known to support life')
+  mars = Planet.new('Mars', 'red', 6.4191e23, 2.279e8, 'Planet with the highest known mountain in its solar system - Olympus Mons')
+
+  solar_system.add_planet(earth)
+  solar_system.add_planet(mars)
+
+  # intro to CLI interface
+  puts '+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+'
+  puts 'WELCOME TO CLISSIN (Command Line Interface Solar System Info Navigation)!'
+  puts '+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+'
+  puts '|                              MENU SELECT                              |'
+  puts '|_____Please enter the NUMBER corresponding to your desired action:_____|'
+  puts '|1. LIST PLANETS CURRENTLY IN SOLAR SYSTEM                              |'
+  puts '|2. OBTAIN DETAILS ON A PLANET CURRENTLY IN SOLAR SYSTEM                |'
+  puts '|3. ADD A PLANET TO THE SOLAR SYSTEM                                    |'
+  puts '|4. FIND THE DISTANCE BETWEEN TWO PLANETS (IF LINED UP IN STRAIGHT LINE)|'
+  puts '|5. EXIT                                                                |'
+  puts '+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+'
+  print "Enter your selection: "
+  user_input = gets.chomp.to_i
+
+  while user_input != 5 do
+    case user_input
+    when 1 # list planets
+      puts "---------------------------"
+      puts "LISTING PLANETS ..."
+      puts solar_system.list_planets
+      puts "---------------------------"
+    when 2 # planet details
+      puts "---------------------------"
+      puts "GETTING PLANET DETAILS ..."
+      planet_det = get_planet_detail(solar_system)
+      puts planet_det.summary
+      puts "---------------------------"
+    when 3 # add planet
+      puts "---------------------------"
+      puts "ADDING PLANET ..."
+      user_add_planet(solar_system)
+      puts "---------------------------"
+    when 4 # distance between two planets
+      puts "---------------------------"
+      puts "GETTING DISTANCE BETWEEN TWO PLANETS ..."
+      distance_info = user_input_distance(solar_system)
+      puts "Assuming they are lined up in a straight line, the distance between %s and %s is %.2f" % distance_info
+      puts "---------------------------"
+    when 5 # exit case
+      break
+    else # invalid input
+      print "INVALID INPUT. "
+    end
+    puts "CURRENTLY YOU CAN:\nEnter 1 to LIST PLANETS\nEnter 2 to GET PLANET DETAILS\nEnter 3 to ADD A PLANET\nEnter 4 to FIND THE DISTANCE BETWEEN TWO PLANETS\nEnter 5 to EXIT"
+    print "Select an option: "
+    user_input = gets.chomp.to_i
+  end
+
+  puts "Thank you for using CLISSIN. See you Space Cowpoke!"
+
+end
+
+main
\ No newline at end of file
diff --git a/lib/planet.rb b/lib/planet.rb
new file mode 100644
index 00000000..58727670
--- /dev/null
+++ b/lib/planet.rb
@@ -0,0 +1,34 @@
+# Pauline Chane (@PaulineChane)
+# Ada Developers Academy C14
+# Solar System Assignment - planet.rb Planet Class
+# 09/23/2020
+
+# Planet class object
+class Planet
+  # readable access
+  attr_reader :name, :color, :mass_kg, :distance_from_sun_km, :fun_fact
+
+  # constructor
+  def initialize(name, color, mass_kg, distance_from_sun_km, fun_fact)
+    # so since i can't raise an error while assigning a field,
+    # going to do that here for @mass_kg and @distance_from_sun_km
+    raise ArgumentError, "Invalid @mass_kg input - must be greater than zero" unless mass_kg > 0
+    raise ArgumentError, "Invalid @distance_from_sun_km input - must be greater than zero" unless distance_from_sun_km > 0
+
+    # assign fields if no errors raised
+    @name = name
+    @color = color
+    @mass_kg = mass_kg
+    @distance_from_sun_km = distance_from_sun_km
+    @fun_fact = fun_fact
+  end
+
+  # addtl accessors/readers
+  # returns formatted summary of planet info.
+  def summary
+    # generally, we don't want to put puts statements in class/instance methods.
+    # puts doesn't return a string that we could potentially need to use in something else.
+    # puts will also risk giving us unwanted output in some cases.
+    return "SUMMARY OF PLANET\nPLANET: #{@name}\nCOLOR: #{@color}\nMASS (KG): #{@mass_kg}\nDISTANCE FROM SUN (KM): #{@distance_from_sun_km}\nFUN FACT: #{@fun_fact}"
+  end
+end
diff --git a/lib/solar_system.rb b/lib/solar_system.rb
new file mode 100644
index 00000000..d9e15fdd
--- /dev/null
+++ b/lib/solar_system.rb
@@ -0,0 +1,56 @@
+# Pauline Chane (@PaulineChane)
+# Ada Developers Academy C14
+# Solar System Assignment - solar_system.rb Solar System Class
+# 09/23/2020
+
+# Solar System class object
+class SolarSystem
+  # field accessors/readers
+  attr_reader :star_name, :planets
+  # constructor
+  def initialize(star_name)
+    @star_name = star_name
+    @planets = []
+  end
+
+  # other accessors/readers
+  # list all planets in @planets array, return as string
+  def list_planets
+    planet_list = "Planets orbiting #{@star_name}"
+    (0...@planets.length).each do |i|
+      planet_list += "\n#{i + 1}. #{@planets[i].name}"
+    end
+    return planet_list
+  end
+
+  # returns instance of Planet object in @planet that has matching (not case sensitive) planet.name to input string
+  # if multiple planets have same name in @name field, returns first instance
+  # if no planets match, returns nil
+  def find_planet_by_name(planet_name)
+    return @planets.detect{|planet| planet.name.downcase == planet_name.downcase}
+  end
+
+  # returns, assuming all planets are in lined up a straight line, distance between two planets (absolute value)
+  # as noted by two input parameters (two planet names)
+  # if neither planet is found in SolarSystem object, returns nil
+  def distance_between(planet_name1, planet_name2)
+    planet1 = self.find_planet_by_name(planet_name1)
+    planet2 = self.find_planet_by_name(planet_name2)
+
+    return planet1.nil? || planet2.nil? ? nil : (planet2.distance_from_sun_km - planet1.distance_from_sun_km).abs
+  end
+
+  # mutators
+  # add planet to @planets array
+  # returns true upon successful addition of Planet object
+  # otherwise, nothing is added and function returns false
+  def add_planet(planet)
+    if planet.is_a?(Planet)
+      @planets << planet
+    else
+      return false
+    end
+    return true
+  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..ffb3d798
--- /dev/null
+++ b/test/planet_test.rb
@@ -0,0 +1,99 @@
+# Pauline Chane (@PaulineChane on GitHub)
+# Ada Developers Academy Cohort 14
+# Solar System Optional Exercise - Planet Class Minitests
+# 09/23/2020
+
+# Practice TDD by writing tests to validate functionality for two new classes: Planet and SolarSystem
+
+require 'minitest'
+require 'minitest/spec'
+require 'minitest/autorun'
+require 'minitest/reporters'
+require 'minitest/pride'
+
+require_relative '../lib/planet'
+
+Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
+
+describe 'Planet' do
+
+  it 'creates a new Planet object' do
+    # Arrange and Act
+    earth = Planet.new('Earth', 'blue-green', 5.972e24, 1.496e8, 'Only planet known to support life')
+
+    # Assert
+    expect(earth).must_be_instance_of Planet
+  end
+
+  it 'can read all field inputs for a created Planet object' do
+    # Arrange and Act
+    earth = Planet.new('Earth', 'blue-green', 5.972e24, 1.496e8, 'Only planet known to support life')
+
+    # Assert for each field
+    expect(earth.name).must_equal 'Earth'
+    expect(earth.color).must_equal 'blue-green'
+    expect(earth.mass_kg).must_be_close_to 5.972e24
+    expect(earth.distance_from_sun_km).must_be_close_to 1.496e8
+    expect(earth.fun_fact).must_equal 'Only planet known to support life'
+  end
+
+  it 'can print a summary of all fields assigned for a Planet object' do
+
+    # Arrange and Act
+    earth = Planet.new('Earth', 'blue-green', 5.972e24, 1.496e8, 'Only planet known to support life')
+
+    earth_summary = earth.summary
+    # Assert <-  You do this part!
+    expect(earth_summary).must_equal "SUMMARY OF PLANET\nPLANET: #{earth.name}\nCOLOR: #{earth.color}\nMASS (KG): #{earth.mass_kg}\nDISTANCE FROM SUN (KM): #{earth.distance_from_sun_km}\nFUN FACT: #{earth.fun_fact}"
+  end
+
+  it 'raises an ArgumentError for mass_kg construction parameter input less than or equal to 0' do
+    # error for 0
+    expect {
+      Planet.new('Earth', 'blue-green', 0, 1.496e8, 'Only planet known to support life') # 24
+    }.must_raise ArgumentError
+    # error for less than 0
+    expect {
+      Planet.new('Earth', 'blue-green', -1, 1.496e8, 'Only planet known to support life') # 24
+    }.must_raise ArgumentError
+  end
+
+  it 'raises an ArgumentError for distance_from_sun_km construction parameter input less than or equal to 0' do
+    # error for 0
+    expect {
+      Planet.new('Earth', 'blue-green', 5.972e24, 0, 'Only planet known to support life') # 24
+    }.must_raise ArgumentError
+    # error for less than 0
+    expect {
+      Planet.new('Earth', 'blue-green', 5.972e24, -1, 'Only planet known to support life') # 24
+    }.must_raise ArgumentError
+  end
+
+  it 'raises an NoMethodError when user attempts to write/mutate Planet fields, ex) planet.color = \'pink\'' do
+    # Arrange and Act
+    earth = Planet.new('Earth', 'blue-green', 5.972e24, 1.496e8, 'Only planet known to support life')
+
+    # Assert
+    # catch error for attempts to write in all fields as user
+    expect {
+      earth.name = "Not Earth"
+    }.must_raise NoMethodError
+
+    expect {
+      earth.color = "lava red"
+    }.must_raise NoMethodError
+
+    expect {
+      earth.mass_kg = "1000000"
+    }.must_raise NoMethodError
+
+    expect {
+      earth.distance_from_sun_km = "1000000"
+    }.must_raise NoMethodError
+
+    expect {
+      earth.fun_fact = "Mostly harmless."
+    }.must_raise NoMethodError
+  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..efe97fd8
--- /dev/null
+++ b/test/solar_system_test.rb
@@ -0,0 +1,108 @@
+# Pauline Chane (@PaulineChane on GitHub)
+# Ada Developers Academy Cohort 14
+# Solar System Optional Exercise - SolarSystem Class Minitests
+# 09/23/2020
+
+# Practice TDD by writing tests to validate functionality for two new classes: Planet and SolarSystem
+
+require 'minitest'
+require 'minitest/spec'
+require 'minitest/autorun'
+require 'minitest/reporters'
+require 'minitest/pride'
+
+require_relative '../lib/solar_system'
+require_relative '../lib/planet'
+
+Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
+
+describe 'SolarSystem' do
+
+  it 'creates a new Solar System object' do
+    # Arrange and Act
+    solar_system = SolarSystem.new('Sol')
+
+    # Assert
+    expect(solar_system).must_be_instance_of SolarSystem
+  end
+
+  it 'can add ONLY Planet object to @planets' do
+    # Arrange and Act
+    solar_system = SolarSystem.new('Sol')
+    earth = Planet.new('Earth', 'blue-green', 5.972e24, 1.496e8, 'Only planet known to support life')
+
+    # Assert for each field
+    expect(solar_system.add_planet(earth)).must_equal true # adds planet
+    expect(solar_system.add_planet(["earth"])).must_equal false # doesn't add non-Planet object
+  end
+
+  it 'can return a string that contains a list of planets in @planets' do
+
+    # Arrange and Act
+    solar_system = SolarSystem.new('Sol')
+    earth = Planet.new('Earth', 'blue-green', 5.972e24, 1.496e8, 'Only planet known to support life')
+    solar_system.add_planet(earth)
+
+    # Assert <-  You do this part!
+    expect(solar_system.list_planets).must_equal "Planets orbiting #{solar_system.star_name}\n1. #{earth.name}"
+  end
+
+  it 'can find a planet in the @planets array of a SolarSystem object by the planet\'s name field' do
+    # Arrange
+    solar_system = SolarSystem.new('Sol')
+    earth1 = Planet.new('Earth', 'blue-green', 5.972e24, 1.496e8, 'Only planet known to support life')
+    earth2 = Planet.new('Earth', 'blue-green', 5.972e24, 1.496e8, 'Has humans')
+    # earth2 verifies that the first occurrence of a planet with name "Earth" is what is returned
+
+    solar_system.add_planet(earth1)
+    solar_system.add_planet(earth2)
+
+    # Act
+    found_planet1 = solar_system.find_planet_by_name('Earth') # first occurrence/exact name match
+    found_planet2 = solar_system.find_planet_by_name('eArTh') # catch cases
+    found_planet3 = solar_system.find_planet_by_name('mars') # not found, should return nil
+
+    # Assert
+    expect(found_planet1.fun_fact).must_equal 'Only planet known to support life'
+    expect(found_planet2.name).must_equal 'Earth'
+    expect(found_planet3).must_be_nil
+  end
+
+  it 'can find, assuming all planets are in a straight line, the distance between two planets in a SolarSystem object as input by name' do
+    # Arrange
+    solar_system = SolarSystem.new('Sol')
+    earth = Planet.new('Earth', 'blue-green', 5.972e24, 1.496e8, 'Only planet known to support life')
+    mars = Planet.new('Mars', 'red', 6.4191e23, 2.279e8, 'Planet with the highest known mountain in its solar system - Olympus Mons')
+
+    solar_system.add_planet(earth)
+    solar_system.add_planet(mars)
+
+    # Act
+    mars_earth_distance = solar_system.distance_between("earth", "mars") # not case sensitive!!
+    earth_klaatu_nebula_distance = solar_system.distance_between("earth", "klaatu nebula")
+
+    # Assert
+    expect(mars_earth_distance).must_be_close_to 78300000.0
+    expect(earth_klaatu_nebula_distance).must_be_nil
+  end
+
+
+  it 'raises an ArgumentError for attempts to write variables into fields' do
+    #Arrange and Act
+    solar_system = SolarSystem.new('Sol')
+    earth = Planet.new('Earth', 'blue-green', 5.972e24, 1.496e8, 'Only planet known to support life')
+
+    solar_system.add_planet(earth)
+
+    # Assert
+    # catch error for attempts to write in all fields as user
+    expect {
+      solar_system.star_name = "Sokor"
+    }.must_raise NoMethodError
+
+    expect {
+      solar_system.planets = [earth]
+    }.must_raise NoMethodError
+  end
+
+end
\ No newline at end of file