The art is good and really cute, and it's a neat idea, but the controls are way too complicated. There's no real point to pressing a key to put the box in the elevator, then another key to put the guy who brought the box into the elevator. You're gonna do both of those things the second they reach the elevator, since there's nothing really else to do. Both of them should really be automatic, and you should just have to press Space to send your guys out to collect/deliver boxes.
And I get that logically, up and down/W and S are for making the WEIGHT go up and down, but intuitively, you're looking at the elevator, and responding to its movement and position in the building, not the numbers on the side. It should probably be reversed.