diff --git a/main.rb b/main.rb
new file mode 100644
index 00000000..caeb11d9
--- /dev/null
+++ b/main.rb
@@ -0,0 +1,96 @@
+require_relative "planet"
+require_relative "solar_system"
+
+def main
+  # Solar System Setup
+  system = SolarSystem.new("Sun")
+
+  earth = Planet.new('Earth', 'blue-green', 5.972e24, 1.496e8, 'Only planet known to support life')
+  mars = Planet.new('Mars', 'red', 6.39e23, 2.279e8, 'Once had water! Might still?')
+
+  planets = [earth, mars]
+
+  planets.each do |planet|
+    system.add_planet(planet)
+  end
+
+  # CLI
+  menu_options = ["list planets", "planet details", "add planet", "exit"]
+  user_input = ""
+  until user_input == "exit"
+    puts "\nWhat would you like to do next?"
+    puts menu_options.join("\n")
+    user_input = gets.chomp.downcase
+    case user_input
+    when "list planets"
+      puts "\n#{system.list_planets}"
+    when "planet details"
+      planet_details_by_name(system)
+    when "add planet"
+      get_new_planet_details(system)
+    when "exit"
+      puts "\nexiting solar system"
+    else
+      puts "\nplease enter an option from the menu."
+    end
+  end
+
+end
+
+def planet_details_by_name(system)
+  puts "\nWhat is the name of the planet you would like to learn about?"
+  planets = system.planets
+  valid_input = false
+  until valid_input == true
+    planet_name_input = gets.chomp.capitalize
+    valid_input = planets.any? { |planet| planet.name == planet_name_input }
+    if valid_input == true
+      puts "\nDetails for #{planet_name_input}:"
+      planet_to_display = system.find_planet_by_name(planet_name_input)
+      puts "#{planet_to_display.summary}"
+    else
+      puts "\nPlanet not found - please input a different planet name:"
+    end
+  end
+end
+
+def format_detail(required_format, input)
+  case required_format
+  when "string"
+    return input.to_s
+  when "number"
+    return input.to_f
+  else
+    raise ArgumentError.new("Invalid input")
+  end
+end
+
+def get_new_planet_details(system)
+  puts "Please enter all information about this new planet."
+  request_details = {
+    # to_s, or String? ???
+    "name" => {format: "string", request: "name"},
+    "color" => {format: "string", request: "color"},
+    "mass_kg" => {format: "number", request: "mass in kilograms"},
+    "distance_from_sun_km" => {format: "number", request: "distance from the solar system center in kilometers"},
+    "fun_fact" => {format: "string", request: "fun fact"}
+  }
+
+  new_planet_details = {}
+
+  request_details.each do |detail, info|
+    input = ""
+    until input != ""
+      puts "Planet #{info[:request]}:"
+      input = gets.chomp
+    end
+    new_planet_details[detail] = format_detail(info[:format],input)
+  end
+  system.add_planet(Planet.new(new_planet_details["name"], \
+    new_planet_details["color"], \
+    new_planet_details["mass_kg"], \
+    new_planet_details["distance_from_sun_km"], \
+    new_planet_details["fun_fact"]))
+end
+
+main
diff --git a/planet.rb b/planet.rb
new file mode 100644
index 00000000..c852b9b7
--- /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.capitalize
+    @color = color
+    @mass_kg = mass_kg
+    @distance_from_sun_km = distance_from_sun_km
+    @fun_fact = fun_fact  
+  end
+  def summary
+    return "#{@name.upcase} is #{@color}. It is "\
+      "#{@distance_from_sun_km.round} km away from the sun, and "\
+      "has a mass of #{@mass_kg.round} kg. #{@fun_fact}"
+  end
+end
diff --git a/solar_system.rb b/solar_system.rb
new file mode 100644
index 00000000..3dcc2d83
--- /dev/null
+++ b/solar_system.rb
@@ -0,0 +1,23 @@
+class SolarSystem
+  attr_reader :planets
+  def initialize(star_name)
+    @star_name = star_name
+    @planets = Array.new
+  end
+
+  def add_planet(planet)
+    @planets << planet
+  end
+
+  def list_planets
+    return \
+      "Planets orbiting #{@star_name}\n" + \
+      @planets.map.with_index {|planet,index| "#{index + 1}: #{planet.name}"}.join("\n")      
+  end
+
+  def find_planet_by_name(planet_name)
+    planet_name = planet_name.capitalize
+    @planets.find { |planet| planet.name == planet_name }
+  end
+
+end