Sum Grid Game
Select a consistent subset of grid numbers to reach simultaneous sum targets.
Math puzzle challenges
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Help, keyboard and saved progress
Tap tiles or number boxes. Tab moves between fields and buttons; Enter in a field checks the current answer. Undo restores the most recent edit. Hints and Undo mark assistance.
Puzzle progress saves in your browser when available.
Daily puzzles switch at midnight UTC. Best scores are recorded separately for each difficulty.
The Sum Grid Challenge
The board contains positive whole-number entries. Tap a square to select it, or tap again to remove it. A selected value contributes to both its horizontal row and its vertical column. Your job is to choose a set of entries so every displayed row target and column target is exactly met at the same time.
Unlike a simple one-row addition quiz, Sum Grid is a linked constraint puzzle. Choosing one cell may help its row while pushing its column too high. That interaction is the main challenge. Easy uses a compact 3 by 3 grid; Normal and Hard increase the number of interacting targets and adjust the numerical values.
The rules do not require using a predefined number of cells or selecting a particular hidden pattern. Any subset that satisfies all the printed totals passes. Check answer reports a specific row or column total when your selection is inconsistent, so you can improve your arithmetic without revealing the whole solution.
Worked Example with Shared Totals
Consider a 2 by 2 demonstration grid with the values 2 and 5 on the first row and 3 and 4 on the second. Suppose row targets are 2 and 4, while column targets are 2 and 4. Selecting only the upper-left 2 and lower-right 4 works because the row totals are 2 and 4 and the column totals are 2 and 4.
Choosing the upper-right 5 is impossible for that demonstration because it already exceeds the first-row target of 2. This gives a useful shortcut for positive-number grids: whenever a candidate entry is greater than its entire row target or column target, it cannot be selected. This is deduction, not trial and error.
After making a few selections, calculate the remaining deficit for each row and column. If a row needs exactly 3 more and only one unselected value of 3 is available there, that square is forced. Because every selection affects two targets, revisit the intersecting column before committing the next move.
Rules, Tips, Daily Play and FAQs
Use the highlight color to recognize which values are currently counted. Selected squares also announce their state to assistive technology. Check the totals carefully; an individual row that appears right is not enough if a connected column fails. A hint marks a cell from one valid solution and scores the round as assisted.
Can more than one selection solve a board? Sometimes. That is intentional; every mathematically valid set passes. Is there a penalty for checking early? An incorrect check costs points, but the board stays playable. Undo restores the last selection and allows you to test a different approach.
Daily challenges use the date in UTC for a repeatable puzzle. Practice creates new puzzles and retains the current attempt locally when browser storage is available. This game supports mental addition, systematic reasoning, and simultaneous row-column constraints.