Fun game and I loved the art! I managed to beat this in 86 seconds for my high score.
The hit-boxes felt a little off to me, as though they were larger than the sprites are. In a precision platformer like this one it can be tough to find the exact right spot to jump when it's not obvious where you're hitting the obstacles.
I think there's a bug in the part with the 3 horizontal spikey hallways. On many runs the spikes became a bit out of sync with each other (either due to dying on them or the fast-forward mechanic. This made the section seemingly impossible and I'd need to restart the game.
Overall, good job, and I'd love to see more games from you.