Hi I managed to play it on linux using Wine. Your game runs almost fine but with some sudden frame skips that could be a Wine issue itself not sure about that. First impression is:

1) It can use some soothing music in the background, seems that you're going for that look/feel.

2) The box or dice I think should have more prominent edges.

3) The yellow portion looks really barren, if you can mix it up with hole/bricks of different shades of brown and yellow,it'd be really great; since it and the sky covers a major portion of the screen. Also some clouds or mixed grass shades!

4) The bubble that points the direction of the box needs to be more prominent because it's almost invisible against the light blue sky. Maybe a different colour perhaps.

5) I don't know if this is a wine issue or a texture issue but the game looks a bit blurry to me? Like the sharpness  should be more. And is there supposed to be some text in this part? (This could be due to a missing font if it's a Windows only font)

6) I might be missing something but is there a way to recharge the jump like boosting to make longer jumps?

7) The game is hard because it's hard to control arbitrary rotational motion of a box since the edges provide a diagonal force to it but I can only control motion on its centre of axis. There is certainly some mechanic to it like aiming straight up or slight deviation from 90 degree axis to make short jumps,aiming at edges to make longer etc. If you're going for the "all at one go" type level at least implement a save feature where one can save a particular state of the box and just return to it. Otherwise as it now is, it becomes a bit frustrating to do the same thing again and again just for a slight wrong jump. Again this would be fine if I could control more motion of the box. The "save game" feature,imo, will not compromise the difficulty aspect of the game and will keep it fun. The levels as is, are certainly doable, but needs many tries to get everything perfect. In my case I reached somewhat almost at the top after like 20+ tries (>= half of them were random and not really trying,lol!) then just freely fell to the starting point. :)

Overall I enjoy pixel graphics game and soothing games like this. And it's a good project that came out in just 4 days! This comes from a player's perspective and in my opinion those improvements will be really great for the game! Thanks :) 

Btw can I post feedback here, I'm new to the forums?