Way too hard.
I'm giving this a lower score than I normally would, I mean the art is nice, but the lines are WAY too small, I have an optical mouse not a roller ball one, and it's just way too... I dunno... it doens't handle the way it should so sometimes it moves up when I slide it right before it slides right or such, and so I fail the level I managed to SOMEHOW get to level 5 but couldn't get any further, you really need to put in a 'level skip' option or increase the width to make it just a wee bit more doable.