Quite a challenging little platformer. There are couple spots that just took a lot trying, but eventually got. I'd say this game took me a little over an hour. I was looking for secrets, XD.
You've done a good job of steadily introducing mechanics of both what my character is capable of, and actual difficulty and new things in levels. I wish that once I've unlocked those skills, they stay unlocked when I went back to replay previous versions.
Three comments I have for this version, that maybe aren't in your steam release, since it'll be bigger:
FIRST, the embedded game in Newgrounds is set to something that appears larger than 1920x1080 resolution, as such I don't see about 4 to character lengths to the left or right, or top or bottom. There were several levels that were quite difficult because the page keeps going beyond my screen but I can't scroll to it. Just make sure you're accounting for different screen sizes :)
SECOND, is that ESC menu took me back to level select and was pause/resume. I'd like to have some other to get back to the main menu where I could access what the controls where, or put a controls button on the level ESC screen, or just make it easier to get to.
THIRD, is that the background appears to be the same in all levels, green at 1-9 and blue at 10-26. Maybe make these a little more different from each other? It sort of feels like this is fine to up level 16 or so, but once you progress beyond the mountain and things start to feel more cave-like, maybe just a bit more different background? The actual game is fun and so my comments are more fine tuning than anything that's take away from the overall experience.
Otherwise, Great Job! I love the game, and I love the music. As always with games I love, I'd like to see more levels and more story :) Which... you're giving us in the steam version.... You Tease...