How to move from easy Sudoku to medium Sudoku

Moving from easy Sudoku to medium Sudoku is one of the most important steps for anyone who really wants to improve.

In easy Sudoku, observation, basic rules, Naked Single and Hidden Single are often enough. In medium Sudoku, however, these techniques may not be sufficient: often you first need to eliminate candidates, then find new certain moves. The grid can get stuck even if you have made no mistakes, simply because more advanced reasoning is needed.

This transition can feel frustrating, but it is also the most interesting part of learning. This is where you start using candidates better, recognizing pairs, eliminating possibilities and reasoning about the relationship between rows, columns and boxes.

In this guide, we will see how to approach the jump in difficulty gradually.

In easy Sudoku, many moves come from cells with a single candidate or from numbers that have only one possible position in a row, column or box.

When you move to medium Sudoku, these moves may no longer be available. You look at the grid, check the most promising cells, but you do not find any certain number to place.

This does not mean you have to guess. It means you probably need to eliminate candidates before finding new moves.

Intermediate techniques are made exactly for this: they do not always place a number immediately, but they reduce the possibilities until new certainties appear.

The real step up in medium Sudoku is learning to use candidates.

At easy levels, you can often manage even without detailed notes. At medium levels, instead, candidates become almost essential, because many techniques are based precisely on their distribution.

You need to learn not only to write candidates down, but also to read them. A cell with two candidates can be important. Two cells with the same candidates can form a pair. Candidates aligned in a box can allow eliminations along a row or column.

Candidates turn the grid into a logical map. The better you manage them, the easier it becomes to see the available techniques.

To handle medium Sudoku, you do not need to learn every existing technique right away. It is better to focus on a small group of useful and frequent techniques.

After Naked Single and Hidden Single, the main techniques to know are:

• Naked Pair;
• Hidden Pair;
• Pointing;
• Claiming;
• Naked Triple.

These techniques cover many typical situations in medium Sudoku. Some eliminate candidates from other cells in a row, column or box. Others narrow the possibilities inside specific cells.

The goal is not to memorize complicated names, but to understand the reasoning behind each technique.

Naked Pair is often the first intermediate technique to learn.

It occurs when two cells in the same row, column or box contain exactly the same two candidates. Those two numbers must occupy those two cells, so they can be eliminated from the other cells in the same unit.

This technique is useful because it is fairly visible. If you use candidates, you can easily recognize two cells with the same pair of numbers.

Practicing Naked Pair gets you used to seeing cells not only individually, but also as connected groups.

Hidden Pair is harder to see because it starts from the numbers, not from the cells.

It occurs when two numbers can go only in the same two cells of a row, column or box. In that case, those two cells are reserved for those numbers, even if they contain other candidates.

The consequence is that you can eliminate from the involved spaces all candidates unrelated to the pair.

This technique helps you read the distribution of numbers in the grid better and not limit yourself to pairs that are already obvious.

Pointing and Claiming work with the relationship between boxes, rows and columns.

Pointing starts from a box: if the candidates of a number in the box are all on the same row or column, you can eliminate that candidate outside the box along that line.

Claiming starts instead from a row or column: if a number can go only inside a certain box, you can eliminate it from the other cells of that box.

These techniques are very important in medium Sudoku because they allow eliminations even when there are no obvious pairs.

Naked Triple is a more advanced version of Naked Pair.

It occurs when three cells in the same row, column or box collectively contain only three candidates. Those three numbers are reserved for those three cells and can be eliminated from the other cells in the same unit.

At first it can seem difficult, because the three cells do not all need to have the same candidates. The important point is that, considered together, they contain only three numbers.

Naked Triple is useful when many cells still have several candidates and you need a deeper cleanup of the possibilities.

To move from easy to medium Sudoku, it is useful to follow a gradual path.

First, make sure you recognize Naked Single and Hidden Single well. Then start training Naked Pair, because it is the most immediate intermediate technique. After that, move on to Hidden Pair, which requires more careful reading of the numbers.

When you feel more confident, study Pointing and Claiming together, because they are connected techniques. Finally, add Naked Triple.

During games, do not immediately look for the hardest technique. You can follow this checking order:

• look for Naked Single and Hidden Single;
• check for possible Naked Pairs;
• look for Hidden Pairs in the most promising units;
• observe interactions between boxes and lines with Pointing and Claiming;
• only after that, look for possible Naked Triples.

On Sudoku Arena, when available, an explained hint can help you understand which technique was useful when you got stuck. The best advice is to read the explanation, go back to the grid and try to recognize the same pattern by yourself in a later game.

Moving from easy Sudoku to medium Sudoku means learning to reason better with candidates.

When Naked Single and Hidden Single are no longer enough, elimination techniques such as Naked Pair, Hidden Pair, Pointing, Claiming and Naked Triple come into play.

The secret is not to rush. Learn one technique at a time, apply it on grids suited to your level and use hints as a learning tool. With an orderly method, medium Sudoku becomes much more readable and less frustrating.