Added texture cache and sprite origins.

AlientAttack.MonoGame/Things/Muzzles/MuzzleMath.cs

@@ -7,7 +7,7 @@ public static class MuzzleMath
     public static Vector2 GetMuzzleWorld(Sprite owner, Vector2 muzzleLocalPx, float ownerScale = 1f)
     {
         // Assumes owner.Position is the top-left of the sprite
-        return owner.Position + muzzleLocalPx * ownerScale;
+        return owner.Position - owner.Origin + muzzleLocalPx * ownerScale;
     }
 
     public static Vector2 CenterBulletOn(Vector2 muzzleWorld, int bulletW, int bulletH)