With WebGL build this game would have much more attention) 
Love such games, puzzles in the pixel-art platforming world are something beautiful. Love the main mechanic but found that you can jump vertically and just replace the block underneath you higher each time) So it needs a lot of polishing. But with a nice level design + controls and character physics, it would be a nice little game for a jam. Good job here!

I didn't expect to like this so much when nobody rated it before me :-) 

But this is a cool little game and if I were you I would remove the "very early build" note. From my POV, this is a proper game jam material, it's nice, it's small and it's fun. If you could provide a WebGL build so it's playable in the browser, I think many more people would play it and enjoy it. 

If you polished the controls a little bit and added some sounds, this would be a great little game.