Clueless Special Guide
As a special service for people new to the Clueless Special, here is an introduction to this format. This page contains an easy Clueless Special, which you can solve with singles only.
A Clueless Special has 9 constituent Sudokus. You can try to solve these puzzles on their own, but you won’t get very far. At some point, you need to pass results from one puzzle to the next. Here’s where the blue cells come into play. Together, the central 3x3 boxes of all 9 Sudokus form a 10th sudoku. The name of this format is derived from the fact that you will not find any initial clues in this 10th puzzle. It is completely clueless.
Start with the clues you receive from the 9 sudokus. Even if you prefer to solve regular Sudokus without pencilmarks, the sheer size of a Clueless will not allow you to remember all eliminations. You can maintain the pencilmarks for the central sudoku in a separate grid.
Take the first sudoku in the starter, for example. On it’s own, you can only solve 17 cells, none of them in the center box. To achieve this, you need several locked candidates, naked pairs, a hidden quad and an X-wing. Brilliant if you manage to find them, but not effective.
A better strategy is to work out the pencilmarks for the central blue 3x3 box.
These are the pencilmarks for the 3 top blue boxes:
Because a 3x3 box in a constituent puzzle is also a 3x3 box in the 10th puzzle, there is no need to look for hidden singles in these boxes again. Concentrate on the rows and columns in the central puzzle. There is a hidden single for digit 1 in the 3rd row. When you cannot find any singles, you may need the boxes to find locked candidates in the central puzzle. Eliminations done in the central puzzle can also be fed back to the constituent puzzles to reveal singles and other goodies.
Make sure that you correctly pass the results between the central puzzle and the 9 constituent puzzles. An error is easily made and hard to detect, until you get stuck hours later. You may have to move back and forth between the 10 puzzles a few times, before you have solved them all.
This is the solution for the Clueless Special starter
These number strings represent each of the 9 constituent puzzles. You can copy each of these 9 strings and paste them in your sudoku program. This allows you to work on each of the 9 constituent puzzles on your computer. A program like SudoCue allows several instances running at the same time.