This puzzle was created by Jakhob and wooferzfg. It is the final puzzle in the uN-Chained Puzzle Pack, which focuses on a Sudoku variant called N-Chains.
An N-Chain is a set of N cells in a row or column that point to each other in a path to form a cycle. Here is an example of a 5-Chain in a row:
The 7 points to column 7, which has a 4.
The 4 points to column 4, which has a 5.
The 5 points to column 5, which has a 3.
The 3 points to column 3, which has a 2.
The 2 points to column 2, which has a 7, completing the 5-Chain.
A pair of colored boxes in a row or column indicates that there is an N-Chain that stays between the boxes and includes both boxes. The length of the N-Chain is given in the top left corners of the boxes. Blue boxes show N-Chains in rows, and red boxes show N-Chains in columns.
Here is a 6x6 example puzzle:
Normal Sudoku and N-Chain rules apply.
Digits in a circle must appear in at least one of the four cells surrounding the circle.
Lösungscode: Row 1 followed by Row 8