Fish

Two-string kite

A two-string kite is a row and a column that each hold a digit in exactly two cells. One cell of the row and one cell of the column sit in the same box, so they can't both be the digit. That means at least one of the other two cells, the far ends, must hold it, and the digit can be removed from any cell that sees both ends: the cell where the row of one end crosses the column of the other.

Written by Georgi Nedyalkov

Level
Advanced

The pattern

Two-string kite: what it does.

Each string is a strong link: the row has the digit in one of its two cells, the column in one of its two. The box is where the two strings are tied together.

The two cells inside the box see each other, so at most one of them holds the digit. If the row's near cell doesn't, the row's far end does; if the column's near cell doesn't, the column's far end does. One of the two is always true.

It's a close relative of the skyscraper. A skyscraper ties two rows together through a shared column; a kite ties a row to a column through a shared box.

Example

Two-string kite: a worked example.

  1. Find the two strings

    Follow one digit and find a row where it can go in exactly two cells, and a column where it can too.

  2. Tie them in a box

    Look for a row and a column where one home of each sits in the same box. They have to be two different cells: a row and a column that share a cell are not a kite.

  3. Read the far ends

    The row's other home and the column's other home are the ends. Both must be outside that box.

  4. Clear the crossing

    Remove the digit from the cell that sees both ends: the one in the row of the column's end and the column of the row's end, if it still has the digit as a candidate.

Spotting it

Two-string kite: how to spot it.

  • Collect the rows and columns with two homes for each digit as you go. Skyscrapers, X-Wings and kites are all made of them.
  • Look at the boxes. A kite is two strings that both pass through one box, one across and one down.
  • The target is easy to find once you have the ends: it's the fourth corner of the rectangle the two ends make with the box.
  • Check that both ends are outside the box. If one of them is inside it, the strings aren't tied at the box and nothing follows.

Where it stops working

A kite clears one cell at most, and that cell often doesn't have the digit anyway, so many kites give nothing. It also needs both strings to be real: a row with a third, forgotten candidate breaks the link and the removal stops being safe.

Keep going

Related topics.

New to sudoku? The rules take two minutes to read, and the first-puzzle walkthrough covers the basics that come before any of these.

Beyond the lessons.

The game's lessons stop at X-Wing, so there's no Two-string kite lesson. The eight it does teach will get you through almost any puzzle; this page is here for when you run into the pattern anyway.

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