(This post is part of the Genuinely Approachable Sudoku (GAS) series.)
Columns 1, 5, and 9 are empty in this Column Indexer Sudoku. Earn your stripes by filling in these columns and the remaining cells of this puzzle.

PDF

or solve online (using SudokuPad)

Theme: 159159

Author/Opus: This is the 182nd 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, the cells marked in red are column indexers. In this puzzle, 1, 5, and 9 are the column indexers. If the number X is in a red cell in column Y in a given row, then in the same row the number Y is in column X. (For example, if in the third row there is a 3 in column 1 in the red column indexer, then the 1 in that row is in column 3; similarly, if there is a 5 in column 4 of the third row, that would mean column 5 of the third row contains a 4 because of where the 5 would be indexed.)

GAS Time Standards (highlight to view): Two party hats (🎩🥳): 8:00; One party hat (🥳): 15:00. All other solvers earn a 🦕: counting Conchoraptor.

Thomas Hits the GAS (highlight to view): 3:03, 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

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.