It’s good, I like it. I think that it might become easier to use if:

- The whole item is clickable for the pick

- Picked state is indicated clearly, possibly by hovering the item

- You click on the item itself to place, or possibly anywhere on the screen

Came to say that it badly needs better state communication.

What I’d do is to add a drop shadow and increase scale by 1-3%, with a clean, snappy animation between placed and picked up. I might also add a “gripping hand” graphic with a cursor-like appearance to picked up items and show a “scroll to move” instruction next to the hand graphic if the user hasn’t done anything for a couple of seconds.