### Nanro (Doubleback) by Takeya Saikachi

**Theme:** Grid Symmetry and Logic

**Author/Opus:** This is the 4th puzzle from guest contributor Takeya Saikachi.

**Rules:** Variation of Nanro and Nanro Signpost puzzles.

Label some cells with numbers to form a single connected group of labeled cells; no 2×2 group of cells may be fully labeled. Each bold region must contain at least one labeled cell. The small clue numbers indicate how many cells in that region are used. When two numbers are orthogonally adjacent across a region boundary, the numbers must be different. **Each bolded region must be visited twice (i.e., have exactly two distinct connected groups inside it).**

Also see this example:

**Answer String:** Enter the length in cells of each of the segments labeled with numbers from left to right for the marked rows, starting at the top. Separate each row’s entry from the next with a comma.

**Time Standards (highlight to view):** Grandmaster = 5:45, Master = 7:15, Expert = 14:30

**Note:** Follow this link for Nanro puzzles on this website and this link for variations on Nanro puzzles. If you are new to this puzzle type, here are our easiest Nanro Puzzles to get started on. More Nanro puzzles can be found in A Number o’ Nanro by Prasanna Seshadri.