Okay so, what I can say is I played a good polished and well designed game, and It's impressive to see such good stuff in a first project
I saw 2 levels and played both of them and the feeds I can give is

-The screen might shake less while moving boxes
-When we keep pressing W (jump), the player might keep jumping too
-Ground / Platform art can be more compatible with background, such as a dirt or grass texture for example.

Other than these, the art also impressed me. It looks cute and pretty. Also movements are very simple and suitable that I didn't even fell in need to read your how to play section Good job, keep going like this!