Divide the grid into "boomerangs", each containing exactly one dot. A "boomerang" consists of a center cell and two legs of equal length coming off the center cell at a 120-degree angle along two different rows (or a row and a column). Each cell in the grid must be part of exactly one boomerang. The legs must be of length at least 1.
(Rules from PGP IB, example from WPC 2018 IB)
History of the puzzle
Invented by Vladimir Portugalov (Belarus) in 2006 and first appeared on Forsmarts issue 18. 
Appearances in the past WPCs
- WPC 2018/Round 4 by Jan Novotný