Extremely difficult. But most of the difficulty is artificial, thanks to the obnoxious mouse controls. If there were an option for keyboard controls, and an indication of where you are in the game so I don't feel like I'm making zero progress and just wasting my time, I might have actually enjoyed this game.
The poor quality of the controls, the monotonous nature of the gameplay, and the lack of information combines to make this an overall unrewarding, unmotivating experience worth taking 2.5 stars over.