How to play
- Goal
- Place gems numbered 1–9 so the edge clues give each row and column's gem count and value sum, and no two gems touch, even diagonally.
- How it ends
- A chart completes when every count, sum and separation rule holds; there is no loss.
- Record
- Your first solve time is kept per chart, and the fastest verified first solve appears with its holder.
- Place gems numbered 1–9. The clue above a column and left of a row is its gem count; the clue below a column and right of a row is its digit sum. Gems may not touch by side or corner. The worked ledger shows gem 2 blocking a diagonal neighbour while gem 3 belongs two rows away.
- Tap a cell to select it, then tap a digit. Tap the same digit or Erase to clear it, or Cross out a cell you know is empty. The edge clues glow when they agree with your marks.
- Undo reverses a mark. Restart clears marks without resetting the clock. Check names conflicting clues and ends public ranking for that attempt. A chart completes when every count, sum and separation rule holds; there is no loss.
Controls
| Tap / click a cell | Select the ledger cell |
|---|---|
| Tap a digit 1–9 | Place or remove that numbered gem |
| Cross out | Mark an empty cell |
| Erase | Clear the selected cell |
| Arrow keys | Move focus through the grid |
| 1–9 | Place a gem at the focused cell |
| X | Cross out the focused cell |
| 0 / Delete | Erase the focused cell |
| Z | Undo the last mark |
| R | Restart without resetting the clock |
| Escape | Close a panel |
All 160 fixed charts have one independently verified answer, are distinct under square symmetries, and require count and diagonal rules for uniqueness. Digits are bounded to 1–9. Private witnesses and solvers do not ship. Progress and reduced motion use morass.grades.v1; sound uses the shared site setting. No ads or analytics run inside the game.
About Grades
In a crystal cavern, an illuminated ledger holds numbered gems. Brass runes count the gems in each row and column; sapphire runes add their values.
Explore 160 original charts from 4×4 to 7×7 in four shelves. Every chart has one independently proved answer, and even diagonal gem contact is forbidden.
The clock starts when you open a chart. Your first solve stays on this device; an uninterrupted first session can set the verified public best time shown with its holder.
