Place a digit from 1 to 9 into each cell of the grid so that same digits do not touch each other, even diagonally. Every digit must have all the digits that are smaller than itself in the eight neighbouring cells, including diagonal ones.
(Rules and example from WPC 2017 IB)
History of the puzzle
First appeared on OAPC 9 (2009).  In the IB, Mehmet Murat Sevim (Turkey) is credited as the originator of this puzzle idea.
Appearances in the past WPCs
- WPC 2017/Round 12 by Deb Mohanty