Thanks for the feedback! There's definitely plenty to improve with the visuals in general.
As for the controls, one theme I've seen coming up in other feedback is that dragging blocks around near the back of the grid (farthest from the camera) can feel a little hard to control, or that the blocks get returned to the table when it felt like they should have locked into the back row. I think it has to do with the camera angle and how I raycast the mouse position to the puzzle's grid (which is very low to the table, while the blocks are tall), but I'm not sure how to improve it without making placing blocks in the *front* of the grid feel equally janky. Having a more vertical camera angle is probably the easiest solution!
Thanks for playing!