The rules
- Fill the board so each row, column and box has every number once.
- A box is the area inside a thick border.
- You can't change the starting numbers.
A worked example: one empty cell
Take a row that already holds 1, 2 and 3, on a board that uses the numbers 1 to 4.
The row needs every number once, and only the 4 is missing. So the empty cell takes the 4.
The hint in Quirk says it the same way: "This row has one empty cell left. It takes the missing number, 4."
Playing it in Quirk
Tap a cell, then a number to fill it.
Pick another number to replace it, or tap Clear to empty it.
Tip: Turn on Notes to remember numbers that might fit; notes don't count as answers.