Wow, this game's an insanely well made one, very impressive. I like that there's multiple collectables, and I think the art of the character on the game over and menu screen adds more personality and flare to the game.
Some improvements you could make would be adjusting the collectable spawning, because there were quite a few collectables that would spawn in unobtainable spots and they were often clipping into the obstacles. I also noticed there were a lot of obstacles where it looked like you could slide under them only to find that you couldn't, it's a bit unclear what you can slide under and that adds a bit of confusion for the player, maybe a bit of frustration too. It was mostly the metal structures that would appear in the centre of the track that confused me when playing, there's a very large gap where it looks like you can slide, yet you bump into it as if it's a solid wall. So perhaps adjust the obstacle or move it down so that there isn't a huge gap there to be confused by.
I would also say maybe make the space bar a jump button too. It's a bit uncomfortable just using the arrow keys, this might be just me, but even still, never hurts to add another key binding.
Other then that, it's good stuff.