An example Double Arrow puzzle: the digits between the circles sum to the two circled ends - 1 + 4 + 6 = 3 + 8.
Double Arrow Sudoku draws a line with a circle at each end. The rule balances the two: the digits on the line between the circles must add up to the sum of the two circled digits. It is a neat twist on Arrow Sudoku, where a single circle holds the total - here the total is shared between two ends.
The rule: the line equals the two circles
Add the two circled digits; the cells along the line between them must add to the same amount. Below, the circles hold 3 and 5 (sum 8), and the two line cells 2 and 6 also add to 8.
Circles 3 and 5 add to 8; the line cells 2 + 6 = 8 match them.
A worked example, step by step
Suppose the two circles are already solved as 3 and 5, and the two line cells between them are still empty.
Step 0. Circles 3 and 5 are placed; the two line cells are empty.
Step 1 - total the circles. Add the ends: 3 + 5 = 8. That is exactly what the two line cells must add up to.
Step 1. The two circles add to 8, so the line must total 8.
Step 2 - list the pairs. Two different digits that add to 8 are {1,7}, {2,6} or {3,5}. Since the row already contains a 3 and a 5 (they are in the circles), that pair is out - leaving {1,7} or {2,6} for the line, a sharp reduction from one balance.
Step 2. The line is {1,7} or {2,6} - the {3,5} pair is ruled out by the circles.
Solving strategy
- Solve the circles first when you can. Two known ends give the line an exact target sum.
- Work it backwards too. If the line cells are known, their total fixes the sum the two circles must share.
- Rule out repeats. Digits already used on the same line, or forced by the circles, trim the list of valid pairs fast.
- Treat it as a cage. Once the target is set, the line is a small sum - the same combination logic as Killer.
Common mistakes
- Including the circles in the line sum. Only the cells between the circles add to the total; the circles are the target, not part of it.
- Assuming the ends are equal. The circles need not match each other - only their sum ties to the line.
- Allowing an impossible repeat. Line digits can only repeat across different rows, columns and boxes.
- Forgetting ordinary Sudoku. Every cell still obeys its row, column and box.
Can I play it here?
Not yet - Double Arrow Sudoku isn't one of the puzzle types SudokuStreak generates for now. But you can learn its rules above, and there's plenty here to sink your teeth into meanwhile:
- Try the closely related Killer, which you can play right now.
- Browse all the Sudoku variants we do offer.
- Or print free puzzles from the printable PDF page.
Where to play it
Double Arrow Sudoku belongs to the arithmetic family and runs on 9×9. It is not one SudokuStreak generates yet - but the deduction it trains is the deduction every Sudoku runs on.
Difficulty and type are two separate dials here: the type sets the extra rule, the level sets how much of the grid you start with. Easy Sudoku leaves 36 of the 81 cells filled, so there is always an obvious next move somewhere; Hard Sudoku leaves 26, where scanning gets you started and then leaves you stranded. Take it at the gentler end while the pattern is still new, and move up once it stops being a fight.