Rules: Divide the grid into grey and white regions so that each region contains exactly one number and this number represents the size of the region in unit squares. Numbers in white cells should be part of a white region, same rule applies for grey numbers. Two regions of the same colour cannot touch each other from the sides.
Background: This is a JPC puzzle, you can see the original page from 15th JPC, 2006. I met that same puzzle in Matus’s set of 11th 24 HPC, named “Double Islands”. I prepared this type only once for Zagreb Open 2011. I gave the name. I’m sorry about this, but I had no other choice.
Example:
Reklamlar
This puzzle appeared as “Shirokabe Kurokabe” (White Wall – Black Wall) in “Puzzle Communication Nikoli” no. 34 (june 1991), and ten years later Naoki Inaba published it under the name “Paakoreeshon” (Percolation). The JPC-name reads “Nishoku Teiru” which means 2-color-theorem.
I found that puzzle right here – http://www.janko.at/Raetsel/Naoki/ParKoreshon.htm
Otto Janko provides a lot of japanese puzzles, especially by Naoki Inabe, so it is very easy to get inspired. At 24HPC I add one more rule (about the 2×2 squares) to make the puzzle more similar to Nurikabe.