(This post is part of the Genuinely Approachable Sudoku (GAS) series.)
A special rule applies in this Sudoku puzzle where each stretch of three straight cells in a region must be divisible by three. Can you figure out the key consequences to solve the puzzle?

PDF

or solve online (using our beta test of Penpa-Edit tools)

Author/Opus: This is the 60th puzzle from Clover, part of the Genuinely Approachable Sudoku (GAS) team.

Rules: Standard Sudoku rules (insert a number from 1 to 9 into each cell so that no number repeats in any row, column, or bold region). Also, within each 3×3 region, each of the three sets of three horizontally adjacent cells or three vertically adjacent cells must have a sum that is divisible by three. For instance, R1C1 + R1C2 + R1C3 is divisible by three and R1C1 + R2C1 + R3C1 is divisible by three. This rule does not necessarily apply across regions.

GAS Time Standards (highlight to view): Two party hats (🎩🥳): 7:00; One party hat (🥳): 13:00. All other solvers earn a 🦕: divisive Diplodocus.

Thomas Hits the GAS (highlight to view): 2:28, with SudokuPad replay file shared as a download for now (requires loading via settings menu with improvements expected before people should use this regularly).

Solution: PDF and solving video with explanation from GAS team.

Note: Follow this link for other less common variations of Sudoku.

Note 2: Comments on the blog are great! For a more interactive discussion, please also consider using our Daily GAS discussion post on the GMPuzzles Discord. Not a member of the Discord? Click this link for basic access.