Pretty damn awesome, but just doesn't cut it.
The gameplay felt smooth. I loved the unique gravity feel it has to it, but jumping between mini-planets within a level would add as a great feature to compare with the first one. But the backgrounds could be better. The songs are fine but a bit out of place, though that's maybe just me.
Also, I find it a bit unfair that if you die, you have to restart all the way from level 1. A save option would do this game justice or at least a way that when you lose you go back to the planet you were in. Also please don't make us re-collect the stars on one level even if we die once. That just becomes repetitive and takes a while to master.
Why is the second level a lot more dangerous than the third? The third doesn't even have danger, it should be the first level IMO. But all in all, the gameplay felt silk smooth and definitely unique. The songs were great but others could probably fit in better, the graphics weren't bad at all. They weren't very simplistic either, but not too detailed, which lead to a great game accessible for everyone.
It's frustrating, fun and unique, but some essential aspects are truly missing, or they're there but don't work very well.