Finished testing and docs for now. Time for new features!

game/spec/universe_array_spec.rb

@@ -18,6 +18,13 @@ RSpec.describe UniverseArray do
       uni_arr[0][0] = 'hi'
       expect(uni_arr[Position.new(0, 0)]).to eq 'hi'
     end
+
+    it 'returns nil when access outside universe' do
+      uni_arr = UniverseArray.new()
+      uni_arr[3] = []
+      expect(uni_arr[Position.new(3, 51)]).to eq nil
+      expect(uni_arr[Position.new(0, 0)]).to eq nil
+    end
   end
 
   describe '#[]=' do