diff --git a/.gitignore b/.gitignore
new file mode 100644
index 00000000..99315534
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/lib/wip.rb
\ No newline at end of file
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..1b70691c
--- /dev/null
+++ b/lib/main.rb
@@ -0,0 +1,68 @@
+require_relative "solar_system/planet"
+require_relative "solar_system/solar_system"
+
+def welcome
+  puts "Welcome to the Solar System app!"
+  puts "================================"
+end
+
+def menu
+  puts "\nWhat would you like to do next?"
+  puts "Please, type the command number"
+  puts "1: list all planets"
+  puts "2: show planet detail"
+  puts "3: add new planet"
+  puts "4: exit"
+end
+
+def get_planet_detail(solar_system)
+  print "\nEnter planet name: "
+  input = gets.chomp
+  found_planets = solar_system.find_planet_by_name(input)
+  if found_planets.length == 0
+    puts "Planet not found."
+  else 
+    found_planets.each do |planet|
+      puts planet.summary
+      puts "============================================="
+    end
+  end
+end
+
+def main
+  welcome 
+
+  solar_system = SolarSystem.new("Sun")
+
+  earth = Planet.new("Earth", "blue-green", 5.972e24, 1.496e8, "Home planet to human race.")
+  earth_2 = Planet.new("Earth", "blue-green-2", 5.972e24, 1.496e8, "Duplicate Earth! Ha-ha!")
+  tatooine = Planet.new("Tatooine", "brown-yellow", 6.4171e23, 23e7, "Though its proximity to the suns makes life difficult, it is located near key hyperspace routes, making it a smuggler and gangster haven.")
+  
+  solar_system.add_planet(earth)
+  solar_system.add_planet(earth_2)
+  solar_system.add_planet(tatooine)
+
+  menu
+  input = gets.chomp
+  
+  while input != "4"
+    case input
+    when "1"
+      puts solar_system.list_planets
+      menu
+      input = gets.chomp
+    when "2"
+      get_planet_detail(solar_system)
+      menu
+      input = gets.chomp
+    when "3"
+      solar_system.create_planet
+      menu
+      input = gets.chomp
+    when "4"
+      break
+    end
+  end
+end
+
+main
\ No newline at end of file
diff --git a/lib/solar_system/planet.rb b/lib/solar_system/planet.rb
new file mode 100644
index 00000000..14e1ce6f
--- /dev/null
+++ b/lib/solar_system/planet.rb
@@ -0,0 +1,18 @@
+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)
+    raise ArgumentError.new("Planet's mass should be greater than zero.") unless mass_kg.respond_to?(:>) && mass_kg > 0 
+    raise ArgumentError.new("Distance from Sun should be greater than zero.") unless distance_from_sun_km.respond_to?(:>) && distance_from_sun_km > 0
+
+    @name = name
+    @color = color
+    @mass_kg = mass_kg
+    @distance_from_sun_km = distance_from_sun_km
+    @fun_fact = fun_fact
+  end
+
+  def summary
+    "\n#{name.upcase}\nColor: #{color}\nMass: #{mass_kg}kg\nDistance from sun: #{distance_from_sun_km}km\nFun fact: #{fun_fact}"
+  end
+end
\ No newline at end of file
diff --git a/lib/solar_system/solar_system.rb b/lib/solar_system/solar_system.rb
new file mode 100644
index 00000000..0c9499a4
--- /dev/null
+++ b/lib/solar_system/solar_system.rb
@@ -0,0 +1,46 @@
+require_relative "../validate"
+
+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 = "\nPlanets orbiting #{@star_name}:\n"
+    @planets.each_with_index do |planet, i|
+      output = output + "#{i+1}. #{planet.name}\n"
+    end
+    return output
+  end
+
+  def find_planet_by_name(planet_name)
+    found_planets = @planets.select { |planet| planet.name.downcase == planet_name.downcase}
+    # raise ArgumentError.new("Unable to find a planet with this name") unless found_planets.length > 0
+    return found_planets
+  end
+
+  def create_planet
+    puts "\nPlease, provide planet data."
+    print "Planet name: "
+    name = gets.chomp
+    print "Planet color: "
+    color = gets.chomp
+    print "Planet mass (kg): "
+    mass = validate(gets.chomp)
+    print "Distance from #{star_name}: "
+    distance = validate(gets.chomp)
+    print "Fun fact (huh?): "
+    fun_fact = gets.chomp
+    
+    new_planet = Planet.new(name, color, mass, distance, fun_fact)
+    add_planet(new_planet)
+    puts "\nPlanet added."
+  end
+end
\ No newline at end of file
diff --git a/lib/validate.rb b/lib/validate.rb
new file mode 100644
index 00000000..c8b49ded
--- /dev/null
+++ b/lib/validate.rb
@@ -0,0 +1,7 @@
+def validate(input)
+  while input !~ /\A[1-9]\d+(\.\d+)?\z/ # positive number
+    print "Please, enter a valid number: "
+    input = gets.chomp
+  end
+  return input.to_i
+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..03cf7aea
--- /dev/null
+++ b/test/planet_test.rb
@@ -0,0 +1,47 @@
+require 'minitest'
+require 'minitest/spec'
+require 'minitest/autorun'
+require 'minitest/reporters'
+require 'minitest/pride'
+
+require_relative '../lib/main.rb'
+
+Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
+
+describe 'Planet' do
+  it 'must raise an error if mass_kg is a negative number' do
+    expect {
+      Planet.new("Earth", "blue-green", -5.972e24, 1.496e8, "Home planet to human race.")
+    }.must_raise ArgumentError
+  end
+
+  it 'must raise an error if distance from Sun is a negative number' do
+    expect {
+      Planet.new("Earth", "blue-green", 5.972e24, -1.496e8, "Home planet to human race.")
+    }.must_raise ArgumentError
+  end
+
+  it 'must raise an error if mass_kg is zero' do
+    expect {
+      Planet.new("Earth", "blue-green", 0, 1.496e8, "Home planet to human race.")
+    }.must_raise ArgumentError
+  end
+
+  it 'must raise an error if distance from Sun is zero' do
+    expect {
+      Planet.new("Earth", "blue-green", 5.972e24, 0, "Home planet to human race.")
+    }.must_raise ArgumentError
+  end
+
+  it 'must raise an error if mass_kg is not a number' do
+    expect {
+      Planet.new("Earth", "blue-green", "a lot", 1.496e8, "Home planet to human race.")
+    }.must_raise ArgumentError
+  end
+
+  it 'must raise an error if distance from Sun is not a number' do
+    expect {
+      Planet.new("Earth", "blue-green", 5.972e24, "I don't know", "Home planet to human race.")
+    }.must_raise ArgumentError
+  end
+end
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