One severe problem. And even with this problem this still deserves 5 stars for just how fucking good it is.
The big problem is that the mouse pointer is not big enough to high lite certain things, the area you select has to be very, very specific. And in addition to this, sometimes your mouse click does not register. I had to re-do the arrow guy multiple times and if I didn't mash on Mouse 1 there was no way I could deflect the arrows.
If this was fixed it would be really enjoyable. As it is it's fun for sure, but not something I would revisit.