I checked it out and the idea behind the game is good, it's just that the implementation can use a few tweaks
It appears that the direction can only be changed in clockwise motion of the mouse, so that is one thing that makes it difficult
That would still work if the targets/bullets were a little slower, since the combination of both of these things make the game nearly unplayable.
Overall, just a few tweaks and this would be a very fun experience!