Variant Sudoku

Skyscraper

When two rows each have exactly two spots for a digit, and one end of each lines up in the same column, any cell that sees both other ends can’t be that digit.

Practice now
4
9
8
3
6
7
3
5
4
6
9
1
8
1
6
8
9
4
4
8
8
5
2
8
1
4
9
8
3
4
8
2
6
3
8
7
2
8
9
8
4
5
4
9
8
8
8
3
8
2
1
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8
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8
9
Clear 8 from cells that see both.

Why it works

On the board above:

Column 2 has only two spots for 8: r6c2 and r7c2. Column 6 also has only two: r6c6 and r8c6.

r6c2 and r6c6 share row 6, so they can’t both be 8.

If r6c2 isn’t 8, then r7c2 is. If r6c6 isn’t 8, then r8c6 is. So r7c2 or r8c6 is 8.

r7c5 sees both r7c2 and r8c6, so it can’t be 8.

How to spot it

  1. Pick one digit

    Look only at that digit’s spots.

  2. Find two rows with exactly two spots

    Columns work the same way.

  3. Line up one end

    One spot from each row sits in the same column. The other two don’t.

  4. Clear cells that see both tops

    Remove the digit from cells that see both of the ends that don’t line up.

Practice

Real boards from the solver, with every pencil mark filled in. Spot it, then use it, then find it cold.

Loading the boards…

Try it in a real puzzle

Each of these needs a Skyscraper to finish. It opens in the player.

Tips

It is an X-Wing with one leg off

If the tops lined up too, you would have an X-Wing.

Look near the tops

The cells that see both tops are usually in the tops’ boxes.

2-String KiteA row and a column each have two spots for a digit, meeting in one box. The cell that sees both far ends loses the digit.Next: 2-String Kite →

In the glossary

Skyscraper