Add initial game code

scripts/GameObjects/Nebula.cs

@@ -0,0 +1,22 @@
+using System.Collections.Generic;
+
+public partial class Nebula : GameObject
+{
+    public List<GameObject> GameObjects { get; private set; }
+
+    public Nebula(string name, CoordinateVector position, CoordinateVector size, GameObject parent)
+        : base(name, position, size, parent)
+    {
+        this.GameObjects = new List<GameObject>();
+    }
+
+    public override void Simulate()
+    {
+        base.Simulate();
+
+        foreach (GameObject gameObject in this.GameObjects)
+        {
+            gameObject.Simulate();
+        }
+    }
+}