How to play
- Goal
- Place two seals and each digit once in every row and column. Each edge clue is the sum strictly between its seals.
- How it ends
- A chart is won when every cell is filled and all line and sum rules hold; there is no loss state.
- Record
- Only the first completed time on each chart can rank; replays keep the first time and are practice.
- Put exactly two seals and each number from 1 through the grid size minus two once in every row and column. The number on each outside edge is the sum of digits strictly between that line’s two seals; digits before the first or after the second do not count. A 0 means the seals touch.
- The worked picture starts with one fixed seal in a row whose clue is 0. Its partner must sit beside it, so the glowing empty square becomes the second seal. Crossing columns then narrow where the digits can go.
- Choose Seal or a number, then tap a square; tap the same mark again to clear it. Undo and Redo repair slips. Restart clears your marks but keeps the first-solve clock. All cells must be filled to finish, and replays cannot change your first time.
Controls
| Tap / click a square | Place the selected seal or digit; tap that mark again to clear it |
|---|---|
| Mark tray | Choose Seal or a number before placing it |
| Arrow keys | Move across the chart |
| 1–3; 0 / X | Place a digit or seal in the selected square |
| Delete / Backspace | Clear the selected square |
| Enter / Space | Place the currently selected mark |
| Undo / U; Redo / R | Step backward or forward through edits |
| Restart | Clear marks without resetting the first-solve clock |
| Escape | Close a panel or return to the atlas |
| Gamepad | D-pad moves; A places, X clears, shoulders change marks, B returns and Start opens settings |
Tips for Doppelblock
- Try a zero If one seal is fixed in a line with clue 0, the second must touch it.
- Count only the gap Digits outside the seals still belong in the line, but do not enter the edge sum.
- Use each digit once After a number appears in a row or column, it cannot appear there again.
Questions about this game
Can seals touch?
Yes. Adjacent seals have no number between them, so their edge clue is 0.
May cells remain blank?
No. Every row and column needs two seals plus every required digit.
Does Restart reset my first time?
No. The clock begins when a chart first opens and keeps running through Restart.
Can I improve my time on replay?
You can replay any chart, but only its first completed time is saved and eligible for the online best.
All 160 pinned charts have distinct clue and given signatures, one independently counted solution, a no-guess deduction trace and another solution if edge sums are removed. Private witnesses never ship. Progress uses morass.doppelblock.v1. Sound follows the shared arcade settings. No ads or analytics run inside the game.
Watch how to play
About Doppelblock
In an enchanted archive, two wax seals hide in every row and column. The digits between them form the sum etched on the edge of the folio.
All 160 original charts are open: 16 small four-by-four introductions and 144 five-by-five folios. Every chart has one independently counted answer and a deduction route that needs no guessing.
Your first completed time stays beside each chart. A first solve on the game page can claim the named online best; later solves are practice.
