Regret

I gave your game a shot. I feel like your movement speed is way too slow. Also the control prompts that pop up seem to be reversed for me. When I'm told to use my right mouse button to do something it was actually my left mouse button that did whatever action like picking up a box or activating the fragments.

Another major place for improvement is your pickup/place mechanic. As it is, the boxes block off most of your view when you're carrying them which makes it hard to line them up. Also they don't stay in a consistent place relative to the player's facing. Take a look at Portal and the way that that game turns the box to line up with you so it doesn't end up at any weird angles. Also possibly consider adding some transparency to the boxes when you pick them up so that the player can see past them.

Lastly, after unlocking the door with the key, the game seemed to end for me. There were no visible object and I was just sort of in space. Couldn't jump or move. Is this actually the end of the game? If not, it's a bug.

Anyways, congrats on releasing your first game!