public static class WorldExtensions
    {
        public static void AddWorldToPlayerLoop(this World world)
        {
            if (ScriptBehaviourUpdateOrder.CurrentPlayerLoop.subSystemList == null)
            {
                // If there were no systems running previously, exit early
                ScriptBehaviourUpdateOrder.UpdatePlayerLoop(world);
                return;
            }

            // Take the previous systems that were running.
            var a = ScriptBehaviourUpdateOrder.CurrentPlayerLoop;

            // Create a player loop from the given world.
            ScriptBehaviourUpdateOrder.UpdatePlayerLoop(world);
            var b = ScriptBehaviourUpdateOrder.CurrentPlayerLoop;

            var result = new PlayerLoopSystem {subSystemList = new PlayerLoopSystem[a.subSystemList.Length]};

            for (var i = 0; i < a.subSystemList.Length; i++)
            {
                var aSub = a.subSystemList[i].subSystemList;
                var bSub = b.subSystemList[i].subSystemList;

                var resultSub = a.subSystemList[i];
                resultSub.subSystemList = new PlayerLoopSystem[aSub.Length + 1];

                for (var j = 0; j < aSub.Length; j++)
                {
                    resultSub.subSystemList[j] = aSub[j];
                }

                for (var j = 0; j < bSub?.Length; j++)
                {
                    // Only add the systems that are specific to the world.
                    // Don't add other systems, they are internal to Unity (e.g. like WaitForTargetFPS).
                    if (bSub[j].type == typeof(SimulationSystemGroup) ||
                        bSub[j].type == typeof(PresentationSystemGroup) ||
                        bSub[j].type == typeof(InitializationSystemGroup))
                    {
                        resultSub.subSystemList[aSub.Length] = bSub[j];
                    }
                }

                result.subSystemList[i] = resultSub;
            }

            ScriptBehaviourUpdateOrder.SetPlayerLoop(result);
        }
    }