I like the pixel art, especially the bag. It felt a bit punishing when I think I only dropped one box I still got the "too low" loosing message. SFX and music would've improved it a lot, but other than that, well done!
Also with the theme being "A special box" it would've been cool having like one golden box that is "worth more" in some way, maybe if you drop it you loose immediately or that you get a bonus when you pick it up.