How to play Sumrex
Six digits, six rules, one sum.
Sumrex is a calm daily logic puzzle. The board is 6×6, divided into six coloured regions, with a digit 1–9 in every cell. Your job: select exactly one cell in each row, each column, and each region — with no two selected cells touching, even at a corner — so the six selected digits add up to today's target.
Each cell cycles on tap: empty → crossed → rex → empty. Use crosses to mark cells you've ruled out — for example, "no rex can have digit 9 if the target is 14, because the five smallest other digits already total 5 + 1 + 1 + 1 + 1 minimums per region". Crosses are scratch paper; only rexes count toward the puzzle.
Press Check once you've placed six rexes. If a rule is broken — two share a row, column,
or region, or two are touching — Sumrex tells you which rule, but never which rex. If the rules
are all met but the sum is off, you'll see by how much. Each Check counts toward the score on your
shareable result, so be deliberate. Reveal solution shows the answer with no penalty;
you'll still get a shareable, marked as revealed.
The twist
Sumrex pairs two constraints that don't normally meet. The placement rules — one rex per row, per column, per coloured region, none touching — narrow the board by deduction. The target sum closes it. Every shipped puzzle has exactly one placement that satisfies both, and is solvable by forced moves alone: no guessing, no backtracking, no "try this and see".
That changes how you play. Most of the deduction is about narrowing rows, columns, and regions until forced moves appear. The sum is a separate, complementary constraint: it caps the largest digit any single rex can hold, and once you've pinned a few rexes it tells you exactly what budget the remaining ones must meet.
Strategy
- Use the sum to bound digits early. Every rex sits in a different row. If today's target is 14 and the smallest digit available in five of the six rows is 1, the sixth rex can be at most 14 − 5 = 9. More usefully: if five rows have a row-minimum of 2, the sixth rex tops out at 4. Cross out everything above that cap in that row.
- Forced cells beat hopeful cells. Look for a row, column, or region where only one cell is still uncrossed. That cell must be a rex. Mark it, then propagate the adjacency rule — its eight neighbours are all crossed.
- Close on the budget. Once four or five rexes are placed, the remaining budget (target minus the placed sum) often pins the last digits exactly. If two rexes are left and the budget is 7, with row-minimums of 3 and 4 in those rows, both rows must take their minimums.
- Crosses are free. Every cross you place narrows the puzzle; mis-placed rexes cost a Check. When in doubt, cross first; place last.
Worked example: the sum bound
Suppose today's target is 12. The grid contains digits 1–9. Six rexes must total 12, no two sharing a row, column, or region, no two touching. Each rex sits in a distinct row, so each row contributes one digit to the sum. Take the minimum digit available in each row — call it the row-minimum. If the row-minimums of five of the six rows total 9, the sixth row's rex can be at most 12 − 9 = 3. Every cell in that row with a digit greater than 3 can be crossed immediately. That single sum-bound step often opens a forced move within seconds.
Frequently asked questions
How do I play Sumrex on mobile?
The whole game lives in a single 6×6 grid that fits comfortably on a 375px-wide screen. Tap a cell to cycle empty → crossed → rex → empty. Buttons sit beneath the grid in thumb reach.
What time does Sumrex reset?
Every puzzle is pinned to 00:00 UTC, so the whole world plays the same Sumrex on the same date.
Are Sumrex puzzles guaranteed solvable by pure logic?
Yes. Every shipped puzzle is generated, then verified by a logic solver that only uses forced-move deductions — no guessing, no search. If a candidate puzzle needs a guess, it's rejected before it reaches the queue.
Why can't I see my mistakes highlighted in green?
By design. Highlighting which rexes are correct would partially solve the puzzle for you on every Check. Sumrex tells you when a rule is broken — adjacency, duplicate row, column, or region — and when the sum doesn't hit the target, but it never points at a specific rex.
More MinCalc games
Enjoyed Sumrex? Try Targle — the target is given, the six-character equation isn't, and you have six guesses to find it. Or Quackle, a 7×7 pond-logic puzzle where each pond holds one connected flock and no two ducks from different ponds sit side by side; Toadle, where you guess the hidden four-letter word in ten tries from one number per guess; or Peerkle, where you rank eight items along a named axis in five attempts.