Medium sudoku
Medium is where you start reading cells instead of units. On every grid here there is a cell that has had all but one digit crossed off it, and no amount of scanning will hand you that digit; a written out candidate list is the only thing that shows it. A grid that never forces one is thrown out during the build, so this is not easy with fewer clues.
Hi! I am Ollie. Welcome to Sudoku Springs!
Every grid here is built to medium and checked against it before you see it. Pencil marks start to pay off. Have fun!
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stone sundial Fill every row, column and box with 1-9. The Stone Sundial board of Sudoku Springs is graded medium, and a level of the trail takes four to six cleared boards.
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terrace steps Fill every row, column and box with 1-9. The Terrace Steps board of Sudoku Springs is graded medium, and a level of the trail takes four to six cleared boards.
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mineral falls Fill every row, column and box with 1-9. The Mineral Falls board of Sudoku Springs is graded medium, and a level of the trail takes four to six cleared boards.
What medium is allowed to ask for
Medium is a narrow window rather than a setting on a dial. A grid is rejected if scanning alone can finish it, and rejected again if finishing it needs a step whose output is candidates struck off other cells.
Grids are built as you play, so this page never runs out, and each one is proved to have exactly one solution before it reaches you.
A medium grid, opened three moves
This is not a drawing. The engine dug it at medium from the fixed
seed opening:medium:0, so it is here tomorrow too, and it reached you with
29 starting digits. These techniques finish it in 52 moves, and the hardest one it forces is a naked single.
Its first 3 moves, in the order the solver makes them. Recompute the candidates from the digits above and you will get the same answer, because nothing below leans on an elimination you cannot see.
- hidden single — In column 5, 1 has only one cell left it can go in. The cell is r5c5, where only 1 and 9 were still legal, so it is 1.
- hidden single — In row 4, 1 has only one cell left it can go in. The cell is r4c9, where only 1, 3 and 6 were still legal, so it is 1.
- hidden single — In row 4, 6 has only one cell left it can go in. The cell is r4c2, where only 3 and 6 were still legal, so it is 6.
The techniques you will meet
Every one of those has a page with a real worked example, generated by the same solver that grades these grids.
The free rung is worth reading twice here, because the technique word in it decides how you look: hidden single means sweep a unit, naked single means stop sweeping and count what one cell has left. The unit named beside it tells you which part of the board that counting belongs in.
Printable sudoku: medium
Each sheet is 12 grids at one level, two to a page, answers at the back. Free, no sign-up, and yours to photocopy for a class.
Other levels: easy, hard, expert.
Under every grid is the first move, in the same words the hint in the game uses: it names the row, column or box to look in and the digit to look for, and never the cell, so it unsticks you at the start without solving anything for you. The answer page names the hardest technique each grid actually needed, measured by the solver that built it. See all four sheets, with a preview of each.
Other levels
- Easy Scan the boxes. No pencil marks needed.
- Hard Needs a pair or a locked digit.
- Expert Goes past the standard techniques. Take your time.
One naked single walked start to finish is on the naked single page, which is the quickest cure for walking past them on a half filled board. When counting candidates stops opening cells for you, hard sudoku starts asking for moves that take candidates away instead of placing digits.