Add initial game code

scripts/GameObjects/Planet.cs

@@ -0,0 +1,35 @@
+using System.Collections.Generic;
+
+public partial class Planet : GameObject
+{
+    public bool IsMoon { get; private set; }
+    public long Diameter { get; private set; }
+
+    public List<GameObject> OrbitingGameObjects { get; private set; }
+    public List<GameObject> PlanetGameObjects { get; private set; }
+
+    public Planet(string name, CoordinateVector position, GameObject parent, bool isMoon, long diameter)
+        : base(name, position, new CoordinateVector(0, 0), parent)
+    {
+        this.IsMoon = isMoon;
+        this.Diameter = diameter;
+
+        this.OrbitingGameObjects = new List<GameObject>();
+        this.PlanetGameObjects = new List<GameObject>();
+    }
+
+    public override void Simulate()
+    {
+        base.Simulate();
+
+        foreach (GameObject gameObject in this.OrbitingGameObjects)
+        {
+            gameObject.Simulate();
+        }
+
+        foreach (GameObject gameObject in this.PlanetGameObjects)
+        {
+            gameObject.Simulate();
+        }
+    }
+}