Add collision detection with octree

EvilSatellites/Quadtree/Positional.cs

@@ -1,10 +1,10 @@
-using System.Numerics;
+using Microsoft.Xna.Framework;
 
 namespace EvilSatellites.Quadtree
 {
     public interface Positional
     {
-        Vector3 Position { get; }
-        Vector3 Dimensions { get; }
+        Vector3 Position { get; set;  }
+        Vector3 Dimensions { get; set;  }
     }
 }

EvilSatellites/Quadtree/Quadtree.cs

@@ -1,5 +1,5 @@
 using System.Collections.Generic;
-using System.Numerics;
+using Microsoft.Xna.Framework;
 
 namespace EvilSatellites.Quadtree
 {

EvilSatellites/Quadtree/QuadtreeNode.cs

@@ -1,6 +1,6 @@
 using System;
 using System.Collections.Generic;
-using System.Numerics;
+using Microsoft.Xna.Framework;
 
 namespace EvilSatellites.Quadtree
 {