Chess Online

The white queen is not gaurding any black escape square that is not already guarded, so it is more or less free to move where it wants, and it's pretty clear that the queen will eventaully effect mate. It's also clear that White needs to keep on checking in order to avoid delaying checks bY Black.
The hard part is identifying the eventual mating square, and in realising the need for the countr-intuitive key move, whose purpose is to force the black bishop onto a square where it will bloack Black's queen.