public void Update(InputState input)
        {
            if (input.WentActive(Keys.F1))
            {
                _dialogMgr.Add(new Prompt(Console.WriteLine));
            }

            AABB selectionBox = new AABB(_selectionBoxP1, _selectionBoxP2);

            int id;
            if (_provinces.TryGetProvinceFromPoint(input.Mouse, out id))
            {
                if (input.WentActive(Buttons.LeftButton) && 
                    _labelClickableBoundaries.ContainsKey(id) &&
                    _labelClickableBoundaries[id].IsPointInside(input.ScreenMouse) &&
                    _units.IsPlayerArmy(id))
                {
                    _unitsSelection.Select(id, input.IsActive(Keys.LeftControl));    
                }
                // Only handle new selections.
                else if (input.WentActive(Buttons.LeftButton))
                {
                    _provinceSelection.Select(id);
                }
                else if (input.WentInactive(Buttons.LeftButton)
                    && selectionBox.Area < _minimumSelectionSize
                    && _unitsSelection.Count > 0)
                {
                    _units.AddOrder(_unitsSelection.Set, id);
                }
                    
                SwapInstrs(_provinceSelection.Hovering);
                _provinceSelection.Hover(id);
                SwapInstrs(id);
            }
            else
            {
                SwapInstrs(_provinceSelection.Hovering);
                _provinceSelection.StopHovering();    
            }

            if (input.WentActive(Keys.G))      MergeSelectedArmies();
            if (input.WentActive(Keys.Escape)) _unitsSelection.DeselectAll();
            if (input.WentActive(Keys.Delete)) DeleteSelectedArmies();

            if (input.WentInactive(Buttons.LeftButton) && selectionBox.Area > _minimumSelectionSize)
            {
                _unitsSelection.DeselectAll();

                // Find all units within the area and select them.
                _labelClickableBoundaries
                    .FindAll(p => _units.IsPlayerArmy(p.Key) && p.Value.Intersects(selectionBox))
                    .ForEach(p => _unitsSelection.Select(p.Key, true));
            }

            UpdateSelectionBox(input);

            if (_unitsSelection.Count > 0)
            {
                Debug.WriteToScreen("Armies", _unitsSelection.Set.Join(", "));    
            }
        }
 public void UpdateSelectionBox(InputState input)
 {
     if (input.WentInactive(Buttons.LeftButton))
     {
         _selectionBoxP1 = Vector2.Zero;
         _selectionBoxP2 = Vector2.Zero;
     } else if (input.WentActive(Buttons.LeftButton))
     {
         _selectionBoxP1 = input.ScreenMouse;
         _selectionBoxP2 = input.ScreenMouse;
     }
     else if (input.IsActive(Buttons.LeftButton))
     {
         _selectionBoxP2 = input.ScreenMouse;
     }
 }