The mechanics were cool and I enjoyed the shifting music. I also like the fact that you added background art which is a nice touch. The platforming felt good , even if a little unforgiving. I also feel it behaved like a platform controller should. Unfortunately I didn't get very far into the game (level 5) because I kept having to restart from 1 after losing lives.
I feel like this game would benefit from a little explanation. Was there a checkpoint somewhere, or was this meant to be played as a full circuit? Maybe giving the players only 1 or 2 lives and then adding a checkpoint every two or three levels would keep players focused. I lost motivation because I wasn't sure if there was a checkpoint. Another option would be giving the player "lives" after each completed round.
Also - I noticed that on level 2 if you die to the jump, there's a fairly good chance that you will respawn and get instantly killed by the bear. Also, if you die to the bear when he's at the far left, you can actually die 3, almost 4 times in a row without moving.
All in all, great job Gapti! I enjoyed the time I spent playing it.