You actually have a great idea in your hands! That was fun! Might I suggest a few things?
First, that artstyle I think it's better for vector art than for pixel art, it will make the game look a lot more smooth.
About the gameplay, the steps to store the box are a bit complicated, like I have to remember the key combinations to open, put the box and close, and by the time I do that, like 4 cubes go by. Maybe Up, Down and P are enough, I think shift complicates things and it also makes me lift my hands off the keyboard to switch from combination to combination since one should be on W and shift, another on P and another on the Up and Down arrow, so I have 3 hands positions and... just 2 hands unfortunately :-( Unless I stretch them in an uncomfortable way I'll be moving hands around and looking at the keyboard a lot. Also, maybe switch P for Enter or right Ctrl? so with one hand I can cover UP, DOWN and ENTER/INTRO/CTRL to store a box. No SHIFT key.
If you read the rest of the comments they're telling you roughly the same, the key combinations make it confusing and/or too hard.
Also, the list.. it's hard to read while you're frantically trying to hit and store boxes. Maybe a pause when adding a new item to the list will help. I mean, it's fair if I lose because I didn't memorize the items, but not because I didn't notice a new item just popped into the list while I was storing a box. Also visual queues on the list might help, like a little green box and a hammer, or a black box and an UP arrow... Not all of us have lightning fast reaction time, some players are faster, others are slower so you need to find a balance between both, otherwise it will get overwhelming at first for a lot of people.
The core mechanic is very fun and the animations are cool, I think you just have to tweak the gameplay to make it more fair, comfortable and fun for everyone. But definitely (despite my observations) a great entry for the jam, good job!