Cool Game
Looked like a mashup between VVVVVV and Sonic at first, obviously because of the gravity shifting and spring-spike elements, but not to say it's a bad thing :)
The engine is solid, haven't seen a bug or a glitch in the hourse spent with this one, the controlls are super-responsive (although C and M wouldn't be my first choise of buttons to use on a laptop- (I was allways messing around with the touchpad).
It's not that hard, but the 'extreme' challenge took me a couple of hours to complete (not it a row, played for several days). It was challenging enough to be worthy of being called a challenge, and fair enough to keep going.
A must-play for any platformer-maniac, especially if you liked V.
Some advice:
It could use an insane challenge like 'collect all the colored blobs, not die AND do it faster than in 400 secs', but that mey just be me.
And the music wasn't that great, you should go for something more upbeat and 8-bit sounding, maybe different melodies for different stage types.