/// <summary>
        /// call this to plan a path between points
        /// </summary>
        /// <param name="begin"></param>
        /// <param name="end"></param>
        /// <returns></returns>
        public Route FindRoute(Location begin, Location end)
        {
            HashSet<MapTile> tilesToReset = new HashSet<MapTile>();//all tiles that need to be reset

            MapTile mapEnd = Map[end.Row, end.Col];
            MapTile mapBegin = Map[begin.Row, begin.Col];
            tilesToReset.Add(mapBegin);

            mapBegin.CostKnown = 0;
            mapBegin.Heuristic = Globals.state.GetDistance(begin, end);
            mapBegin.CostEstimate = mapBegin.CostKnown + mapBegin.Heuristic;

            MinHeap<MapTile> OpenSet = new MinHeap<MapTile>();
            OpenSet.Add(mapBegin);

            while (!OpenSet.IsEmpty)
            {
                MapTile current = OpenSet.ExtractMin();

                if (current == mapEnd)
                    return BuildRoute(mapEnd, tilesToReset);//reset after the oath is build, we need those pi pointers

                foreach (Direction d in (Direction[])Enum.GetValues(typeof(Direction)))
                {
                    Location tile = Globals.state.GetDestination(current.GetLocation, d);
                    MapTile neighbour = Map[tile.Row, tile.Col];

                    bool succesful = Relax(current, neighbour, mapEnd);
                    tilesToReset.Add(neighbour);//hashset will not contain duplicates

                    if (!neighbour.InOpenSet && succesful)
                    {
                        OpenSet.Add(neighbour);
                        neighbour.InOpenSet = true;//openset is a min heap, no O(1) lookup so store this in the tile
                    }
                    else
                    {

                        if (neighbour.InOpenSet && succesful)
                        {
                            OpenSet.ChangeKey(neighbour, neighbour.CostEstimate);
                        }
                    }
                }
            }

            foreach (MapTile t in tilesToReset)//no route found, still need to reset
                t.Reset();

            return null;
        }