I like the visual and the music.
As other have mentioned before, I think the jumping really is tedious here, especially for platformer. Having better control on of the jump and more height and speed to it would help a lot.
The level progression was a little too fast to my taste. I prefer having smaller level that incorporate 1 mechanic at a time, but sometime I sould have to do multiple new things in a level that seems like it should have been 5 level after. The speed of the character also didn't help, since seeing a big level made me think that I would be here for hours :P
In level 3, I got stuck with Redd on the bottom left side of the level, impossible to jump back up or restart the level or go back to the main menu. I also wanted to get the block at the bottom right, but after braving the spikes, I realized that I needed it to get back up and that this whole risky adventure was not even worth it, I was a little sad.
All in all, the visual, music and sfx are polished, but I think the game could benefit from having simpler smaller level.