Add initialPosition property to moons

12/Moon.js

@@ -9,6 +9,14 @@ module.exports = class Moon {
          * The position of the moon in space
          */
         this.position = position;
+        /**
+         * The position of the moon at the time of creation
+         *
+         * This is a silly trick to get a clean copy of the Vector, but it works.
+         *
+         * @private
+         */
+        this._initialPosition = position.negate().negate();
         /**
          * The current velocity of the moon
          */