### Swivelling Serpents [Birthday Surprise] by Prasanna Seshadri

(Note: This bonus puzzle is being posted today to mark the occasion of Prasanna’s birthday.)

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to alternate between a shading mode, a line-drawing mode with diagonal and straight options, and an edge marking mode to add x’s as needed.)

Theme: One Away from Thirty

Author/Opus: This is the 180th puzzle from our contributing puzzlemaster Prasanna Seshadri.

Rules: Locate two snakes in the grid. Each snake must start from one of the gray circles, but has an unknown ending point. Black circles represent an interior cell of one of the snakes, and all black circles must be part of a snake. Each snake’s path is allowed to move vertically, horizontally, or diagonally between cells. An interior snake cell can only be adjacent to two other snake cells (including diagonally adjacent cells) and an end of the snake can only be adjacent to one other snake cell (including diagonally adjacent cells). The two different snakes must not share any adjacent cells.

There are some numbers outside the grid. These numbers indicate the number of vertical or horizontal edges (not corners) that snakes cross in that direction.

There are some letters inside the grid. For each distinct letter, exactly one of its instances is visited by one of the two snakes.

Also see this example:

Solution: PDF

• term says:

Happy Birthday!

• Freddie Hand says:

Nice puzzle! Impressive construction and some interesting logic. Not fully reading the rules really cost me a lot of time, though: V qvqa’g frr gur yvar ‘Oynpx pvepyrf ercerfrag na vagrevbe pryy bs bar bs gur fanxrf’.

Happy birthday Prasanna!

• Walker says:

Happy birthday Prasanna! Really nice puzzle – I’m impressed by how well the clue symmetry works out.

• LorenR says:

Finally solved it! Happy belated birthday! It didn’t really take me over 6 months to solve it since I’ll admit I sort of forgot about it for a while but I printed it at least twice and spent time over the past week on it off and on. Maybe I should retackle “U and I Should Work Together”…

• LorenR says:

Should have mentioned: Great puzzle, as always.

Regards,
Loren

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