Basic Techniques

Single In Box

When there is only one cell in the box which can contain a certain value, this value can be safely assigned
to this cell. Read more...

Single in Row/Column

This technique is based on the fact that every row must contain every value once. Read more...

Moderate Techniques

The following techniques are more difficult to spot because they require that every candidate value is
carefully written down. This is a very timeconsuming and precise task. Fortunately, this task can be
carried out by a computer program. This can spoil the fun of completing the more simple puzzles, but it
can still be very challenging when solving more advanced ones.

Naked Single

After writing down all the candidate values into the cells, you can come across a Naked Single,
which means that there is only one possible value for that cell. Read more...

Pointing Pair

When a specific candidate value inside a box is restricted to one row or column, you can use the Pointing Pair technique.
This means that you can exclude the same candidate value from other boxes in the same row or column.
Read more...

Box Line Reduction

When a specific candidate value in a row or column only occurs in one box, this value can be exluded from other cells in the same box.
Read more...

Advanced Techniques

Advanced Techniques are based on the same principals as the other techniques. They are generally more difficult to spot.
A new term which will be introduced here is the group. A group can be a row, column or box.

Naked Pair

If two cells in the same group contain exactly the same two candidate values, these candidate values can be
excluded from other cells in the group. Read more...

Naked Triple

If three cells in the same group contain exactly the same three candidate values, these candidate values can be
excluded from other cells in the group. Read more...

Naked Quad

If four cells in the same group contain exactly the same four candidate values, these candidate values can be
excluded from other cells in the group. Read more...

Hidden Pair

If two cells in a group contain an identical pair of candidates and no other cells in that
group contain those two candidates, then other candidates in those two cells can be excluded. Read more...

Hidden Triple

If three cells in a group contain an identical pair of candidates and no other cells in that
group contain those three candidates, then other candidates in those three cells can be excluded. Read more...

Very Advanced Techniques

These Very Advanced Techniques require the player to use the whole puzzle, instead of just parts. Sometimes
techniques are chained or multiple techniques can be used together to solve very challenging puzzles.

Remote Pair

When chaining multiple Naked Pairs, a Remote Pair can be used to remove candidate values. Read more...

XWing

This is another method of reducing the candidates when two rows have the same candidate only in the same two columns. Read more...

SwordFish

Generalisation of the XWing pattern. Read more...

XYWing

Generalisation of the XWing pattern. Read more...

XYZWing

Generalisation of the XYWing pattern. Read more...

Empty Rectangles

The Empty Rectangles uses the same logic as the XWing technique te exclude candidate values. Read more...

Colors

When a group contains only 2 of the same candidates, at least one of these candidates must have
this value. By coloring these pairs, candidates can be excluded. Read more...

MultiColors

Generalisation of the Colors technique. Read more...

Nice Loop

Use strong and weak links to exlude candidates or assign values. Read more...

Forcing Chain

Chain pairs to exlude candidates or assign values. Read more...

Bug

Use the information that the puzzle only has one solution to exclude candidate values. Read more...

Unique Rechtangles

Use the information that the puzzle only has one solution to exclude candidate values. Read more...

Guess

Some puzzles cannot be completed using logic steps only. Read more...
