Hurkle Hunt

The Hurkles live in Grdsville (a small community in another dimension). Hurkles are becoming extinct and it is your job to capture as many as possible of the remaining Hurkles for transplantation to other, friendlier locations (like Bayonne, New Jersey). Hurkles are usually invisible and only make brief appearances when startled by the vibrations created when some clod starts trashing their habitat (you for instance). The method you will use to capture the Hurkles is to destroy all the squares surrounding the invisible Hurkles without destroying the square on which the invisible Hurkle is hiding. Using the arrow keys, move the deadly green crosshairs of your genuine handy dandy Ultra-Dimensional Laser Cannon to the rooftop you would like to eliminate forever and press the space bar, Bang!