First game I rated 5/5/5! I didn't make it past level 5 (towns), because being on an AZERTY keyboard I had trouble with the WASD+QE controls and often slammed into islands instead of braking ^^"
I love the art and music, the core mechanic is very good and insanely extensible, and it really makes you (try to) think about what to do next. The only thing I had a gripe with was how you can easily slide into an island you didn't see, either make the movement a bit more "responsive" (i.e. higher acceleration, lower speed cap), and/or add a zoom feature (I found myself trying to scroll out several times) so we can see what tiles lie where, and maybe plot a path that lets us navigate through gaps afterwards.
Congratulations!