EdgeSum
Daily edge-clue logic grid
EdgeSum
Fill the 5x5 grid so every row and column sum matches the edge clues. One unique solution every day, provable by pure logic — no guessing.
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Frequently Asked Questions
How do the sum clues work?
Each row and column has a clue on its edge — the target sum of all filled cells in that row or column. A filled cell contributes a fixed numeric value based on its position, shown faintly inside the cell. Your job is to choose which cells to fill so every row and column sum matches its clue exactly.
Is there always exactly one solution?
Yes. The daily generator runs a solver over every candidate board and only ships boards with a unique solution. You never need to guess — every daily board is deducible by pure logical chains.
What does marking a cell do?
Marking (the X state) has no effect on the sums — it’s a memory aid to track cells you’ve ruled out by deduction. It works like the X marks in Nonogram or Sudoku pencil-marks.
Is the daily board the same for everyone?
Yes. The board is seeded from the current UTC date, so every player worldwide faces the identical puzzle — your tap-count and hint-count are directly comparable with friends.
About EdgeSum
EdgeSum is a daily edge-clue logic puzzle that fuses three classic traditions: Nonogram, Kakuro, and Sudoku. Every day a fresh 5×5 grid arrives with clue numbers along each row and column edge. Each cell in the grid holds a hidden value — your job is to decide which cells to fill so that every row and column total matches its clue exactly. The rules permit only one solving approach: forced-move deductive logic. There is no guessing, no trial-and-error, no backtracking. Every valid EdgeSum puzzle has exactly one solution, machine-verified before it goes live, and every cell placement you make must be provable from the clues alone.
How to play
Tap a cell to cycle its state: empty -> filled -> marked -> empty. Filled cells contribute a value (shown faintly inside each cell) to their row and column sums. Your goal is to match every edge clue. Marked cells are pencil-marks — they don’t contribute to sums, but they help you track what you’ve ruled out. The clue panel beside each row and column turns green when its sum matches.
Why a daily constraint-logic puzzle?
Constraint-propagation puzzles — the family that includes Sudoku, Nonogram, Kakuro, and Hashi — train a specific cognitive skill: one-shot deductive inference. You read all the clues simultaneously, identify which cells are forced, chain those deductions forward, and arrive at the unique solution without ever guessing. This is categorically different from Wordle or Mastermind (which require trial and feedback loops), different from reflex and timing games, and different from spatial path puzzles. The 5×5 format is a deliberate design choice: small enough to finish in a single sitting, yet constrained enough that every puzzle demands the full deductive toolkit. EdgeSum runs entirely in your browser — no account, no ads, no tracking — so the only thing it asks of you is five minutes and a willingness to think. Streak tracking and a daily challenge system give regulars a reason to come back, while the clue-verification step ensures no puzzle ever ships with an ambiguous second solution.