01. Each number is a run of filled squares
Numbers on the left read across their row from left to right; numbers on top read down their column from top to bottom. A 3 means three squares in a row are filled. Where the run starts is decided by looking at the clues on the other lines, too.
This example shows one way to place a 3 in five squares. Without any other clues yet, you can’t pin down where it starts and ends.
02. At least one empty square between runs
If the clue is 2 1, fill two squares, leave at least one empty, then fill one square. The order can’t change. Here is a possible arrangement in a line of five squares.
A clue of 0 means the whole line is empty. An × is your own note that says “this square is definitely empty.”
03. Check across and down together
Every square has to satisfy both its row clue and its column clue. A square you settle in a row becomes a starting point for its column, and an empty square found in a column narrows down the row again.
Stuck at the start? Look for overlaps
Try placing a 3 in five squares as far left as possible, then as far right as possible. In every arrangement, the middle square is always filled.
The empty boxes in the “Certain” line above are squares you don’t know yet. They aren’t necessarily empty, so don’t put an × on them.
When a line fits exactly
If a five-square line has the clue 2 2, then 2 + 1 empty + 2 = 5. You can settle the whole line right away.
Controls on PC and mobile
| What you want to do | How |
|---|---|
| Fill a square | Choose the Fill tool, then click or tap |
| Mark as empty | The × tool or the right mouse button |
| Mark several squares | Press and drag. On mobile, your first direction locks the row or column |
| Clear a mark | Press again with the same tool, or use the Erase tool |
| Keyboard | F fill · X empty · E erase · Arrow keys move · Space/Enter apply |
| Undo | The ↶ button or Ctrl/⌘+Z. Redo with Ctrl/⌘+Y or Shift+Z |
| View big puzzles | Zoom in and out with +/−. Tap ‘Move’ to drag the grid and scroll, then switch back to ‘Mark’ to keep solving |
| Take a break | The Ⅱ button in stage mode. Hiding the tab pauses automatically |
100 stages, at your own pace
There are 20 stages each of Intro 5×5, Easy 8×8, Normal 10×10, Hard 12×12, and Expert 15×15. Every stage is unlocked from the start. Size and clue complexity grow as you go, but puzzles within the same tier can still feel different in difficulty.
Your progress is saved automatically in this browser. A stage hint explains one square that can be logically settled from your current marks. If there’s a contradiction, try undoing first. Whether you used hints is also kept with your completion record.
Meet your first picture →