THE SHORT VERSION
Sudoku: a 9×9 grid, partially filled. Add digits so every row, column, and 3×3 box contains 1–9 exactly once. You place values into empty cells.
Sumplete: an N×N grid, fully filled with digits. Delete some cells so each row and column hits its target sum exactly. You remove values from filled cells.
In Sudoku you're constrained by uniqueness — no digit can repeat. In Sumplete you're constrained by sums — each row and column must hit a target. Neither puzzle requires arithmetic to solve; both are pure logic.
SIDE BY SIDE
Starting state
Sudoku: mostly empty — ~20 pre-filled cells from 81
Sumplete: fully filled — every cell has a digit
Your action
Sudoku: place digits in empty cells
Sumplete: delete digits from filled cells
Constraint type
Sudoku: uniqueness (no digit repeats in row / column / box)
Sumplete: sum targets (each row + column must total its clue)
Arithmetic required
Sudoku: none (1–9 are labels, not values)
Sumplete: light — you compare running totals against targets
3×3 box constraint
Sudoku: yes — the defining third constraint
Sumplete: no — only rows and columns
Finished state
Sudoku: every cell filled; grid partitioned into 81 placed digits
Sumplete: some cells deleted; survivors sum to row/column targets
THE DELETION DIFFERENCE
The key insight in Sumplete is the "deletion amount." Each row has a target sum and a current sum (all digits present). The difference is exactly how much you need to delete from that row. If a row sums to 30 and the target is 18, you must delete digits that total exactly 12.
This creates a completely different first move. In Sudoku you scan for cells where only one digit fits. In Sumplete you scan for rows and columns where the deletion amount forces a specific set of cells to be removed — for example, a deletion of 0 means keep everything; a deletion equal to the row total means delete everything.
Where Sudoku elimination removes candidates cell by cell, Sumplete elimination works across whole rows and columns simultaneously through cross-referencing: a cell deleted from its row must also be deleted from its column, and vice versa.
WHAT TRANSFERS FROM SUDOKU
The elimination mindset carries over directly. In both puzzles, you look for forced moves — situations where only one valid configuration exists — and work outward from there. Neither puzzle rewards guessing.
The row and column scanning instinct transfers too. Sudoku trains you to scan units for the most constrained cells; Sumplete rewards the same instinct applied to deletion amounts rather than digit candidates. Rows with a deletion of zero (keep all) or deletion equal to the total (remove all) are the Sumplete equivalent of a Sudoku naked single.
If you've trained your Sudoku row/column scan, you'll find Sumplete's entry-level grids natural. The difference is at medium and hard difficulty, where the cross-row-column propagation logic has no Sudoku analogue.
WHAT DOESN'T TRANSFER
Sudoku's 3×3 box constraint has no equivalent in Sumplete. The techniques that exploit the box — pointing pairs, box-line reduction, X-wings — don't apply. Sumplete is purely a row-column puzzle.
The uniqueness constraint in Sudoku means you can eliminate a digit from a cell because it already appears in the same row. Sumplete has no uniqueness — the same digit can appear multiple times in a row, and multiple copies might all be kept or all deleted. Sumplete's cross-referencing logic is different enough that it requires a mental reset for experienced Sudoku solvers.
WHICH IS HARDER?
At entry level, Sumplete is typically more approachable. A 4×4 grid with obvious forced keeps and deletes can be solved in under a minute. Sudoku's 9×9 minimum size means even an easy puzzle requires more initial scanning.
At high difficulty, Sumplete on large grids (9×9 or bigger) demands simultaneous row-column accounting that many players find harder than hard Sudoku. The lack of a box constraint means Sumplete doesn't have Sudoku's "pincer" techniques — but the cross-propagation chains on large grids become lengthy and easy to lose track of.
WHEN TO MAKE THE SWITCH
If you play Sudoku: try Sumplete when you want to use your row/column scanning instinct in a different direction. The deletion frame is genuinely novel — the same deductive style, a completely different-feeling puzzle.
If you play Sumplete: try Sudoku when you want a uniqueness-based constraint system that creates longer elimination chains and exploits a third constraint (the 3×3 box) that Sumplete doesn't have.