All Sudoku Variants
9×9 · Arithmetic

Little Killer Sudoku

Arrows outside the grid give the sum of the digits along the diagonal they point to — and on those diagonals, digits may repeat.

4 7 1 4 312

An example Little Killer puzzle: the arrowed diagonal sums to 12 — 4 + 7 + 1 (digits may repeat on the diagonal).

Little Killer Sudoku sets small arrows just outside the grid. Each arrow points along a diagonal, and the number beside it is the sum of every digit on that diagonal. It looks like a cousin of Killer Sudoku, and it is — but with one liberating difference that changes how you solve it entirely: on a Little Killer diagonal, digits are allowed to repeat.

The rule: sum along the arrow

Follow the arrow into the grid and add up the digits in every cell it crosses; that total is the clue. Diagonals can be long (a full corner-to-corner line of nine cells) or short (just one or two cells near a corner). Below, the arrow of clue 15 runs down-right across a five-cell diagonal holding 3, 1, 5, 2 and 4.

15↘31524

The arrow's clue is the diagonal sum: 3 + 1 + 5 + 2 + 4 = 15. Digits on the diagonal may repeat.

How it differs from Killer Sudoku

This is the point that trips up Killer solvers. In Killer Sudoku a cage's digits are all different, so combination logic is tight. A Little Killer diagonal has no such no-repeat rule — because a diagonal crosses several rows, columns and boxes, the ordinary Sudoku rules never force its cells apart. A three-cell diagonal summing to 6 could be 1+2+3, but also 2+2+2 or 1+1+4, provided each digit is legal in its own row, column and box. So think in totals and parity, not in fixed digit sets.

Short diagonals are worth the most

The tightest clues sit near the corners, where a diagonal is only one or two cells long. A one-cell diagonal is a giveaway — the clue simply is that corner digit. A two-cell diagonal summing to 4 is 1+3, 3+1 or 2+2, a tiny set of options. Even a long diagonal helps at its extremes: a nine-cell main diagonal can total at most 45 and at least 45 only if it is a permutation of 1–9, so its sum reveals how much repetition it must contain.

Solving strategy

  • Attack the corners first. One- and two-cell diagonals give digits almost for free.
  • Think totals, not combinations. Repeats are allowed, so reason about the sum and how the row/column/box rules limit each cell individually.
  • Use parity. Whether a diagonal's sum is odd or even constrains how many odd digits it must contain.
  • Feed the grid. A digit fixed by a diagonal behaves like a given for its own row, column and box.

Common mistakes

  • Assuming no repeats. The biggest error — a Little Killer diagonal is not a cage and its digits can repeat.
  • Summing the wrong diagonal. The arrow's direction matters; follow it exactly and include every cell it passes.
  • Forgetting the box still forbids repeats. Digits repeat along the diagonal only when they land in different rows, columns and boxes.
  • Overlooking short lines. The corner diagonals are the fastest way in — do not start with the long ones.

Can I play it here?

Not yet — Little Killer 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: