Detailed placement
Beginner
The final polish: small swaps between nearby parts that make the wires a little shorter.
Novice
Small improvements after legalization: swapping two cells, reordering a few neighbors in a row, or flipping a cell left to right, keeping only the changes that shorten wires and stay legal.
Expert
Moves such as global swap, vertical swap, local reordering of small windows, mirroring and single-segment clustering. Advanced-node detailed placers also fix cell-adjacency rule violations and pin-access conflicts.