Riverbank - Episode 3: Watch on the Rhine

by Henry ‘Pi’ James & Nordy
published on Friday, 6 May 2022

Rules

Normal sudoku: Fill every row, column and marked 3×3 box with the digits 1 to 9 once each.
River & riverbank: Locate a river (think: classic snake) in the grid, consisting of a one-cell wide, non-looping, non-branching string of orthogonally connected cells, which may not touch itself orthogonally (but may diagonally); each border between a river cell and a non-river cell is a riverbank segment (this precludes the grid edge from being counted as riverbank).
Riverbank sweeper: Each circled cell is a riverbank sweeper, which counts riverbank segments within the (up to 3×3) surrounding cells (see example image - but ignore the squared sentinel which is irrelevant for this puzzle).
German whispers: Neighboring cells along the river differ by 5 or more.
No negative constraint: Not all circles are necessarily given.

Riverbank - Episode 3: Watch on the Rhine Riverbank ruleset example

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The riverbank ruleset is based on Borderline by @Jakhob & @wooferzfg.

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