private Node makeNode (int x, int y, boolean passible){        
        if (x >= 0 && x < sizeX){
            if (y >= 0 && y < sizeY){           
                if (map [y][x] == null)
                    map[y][x] = new Node (x, y, this, passible);
                return map[y][x];
            }
        }
        return null;
    }