How to play Sudoku-Layer
Sudoku-Layer combines the logic of non-repeating digits with a board of circles, layers and sums. This guide helps you recognize the groups before making your first move. The examples show a valid completed board; in a game, you fill its missing cells.
1. Five different digits in each circle
The board has nine circles arranged in three rows and three columns. Each circle has five positions: top, bottom, left, right and center. Use digits from 1 to 9, without repeating a digit within that circle.
The Σ symbol marks a fixed target sum. In the example’s top-left circle, the five cells contain 4, 8, 6, 5 and 2. They are different and add up to 25. You do not place all nine digits in one circle: only five that satisfy its sum and the other rules.
Sums differ between circles and between games. A correct sum alone is not enough: the positions also belong to layers and, in some cases, to rows or columns.
2. Follow one position across all nine circles
A layer joins the same position in every circle. For example, the nine top cells form one layer, and the nine center cells form another. There are five layers, each identified by a color. Every layer must contain digits 1–9 exactly once.
In the highlighted top layer, reading left to right and top to bottom, the digits are 4, 5, 9, 1, 6, 2, 7, 3 and 8. If a top cell already contains 4, no other top cell can contain 4. You can customize the colors; the positions and rules stay the same.
3. Rows: left, center and right
In each row of three circles, combine the left, center and right positions of every circle. That gives nine cells in total. This group must contain digits 1–9 without repetition. The top and bottom positions do not participate in this horizontal rule.
The first row in the example contains 6, 2, 5; 8, 9, 1; and 7, 4, 3. All nine digits appear exactly once. A left cell participates in its circle, its left layer and this row.
4. Columns: top, center and bottom
In each column of three circles, combine the top, center and bottom positions of every circle. These nine cells must also contain digits 1–9 without repetition. The left and right positions do not belong to this vertical group.
The first column in the example contains 4, 2, 8; 1, 3, 9; and 7, 6, 5. The center is especially important: it belongs to its circle, the center layer, the row and the column. A center deduction can give information to several groups at once.
Press PLAY when you are ready to begin. Until then, the veil keeps the board locked and the timer at 00:00. You can read guides, configure colors or choose a level without consuming game time. Visiting another page before starting leaves the game ready, without showing “Game paused.” After starting, leaving Sudoku saves the game paused; on return, press Resume or Play.
Playing your first game
Start on Easy. Underlined digits are fixed clues and cannot be changed. Select an empty cell, then press a panel digit or a number key. Before committing, check its circle, layer and relevant row or column. An incorrect entry is not placed and increases the error counter.
Pencil lets you keep up to four candidates per cell. Entering the same candidate again removes it. Notes are possibilities you propose, not answers supplied by the game. Undo reverses the last action, and Pause stops the timer and covers the board. Visiting another site page and returning restores your game in a paused state within the same tab.
Layers shows how many correct cells remain in each position and displays ✓ when its nine digits are complete. The grid beside it marks completed rows and columns. You can open Rules during play, choose your language and adjust colors and audio in Settings. Hint is currently in demonstration mode.
Settings: make the game comfortable for you
Colors help you recognize a layer across the nine circles. Change them for visual comfort, personal preference or if some shades are hard to distinguish, including with color vision differences. This is more than an accessibility option: a palette you recognize quickly also makes the board’s connections easier to follow.
Open Settings, select one of the five positions and choose its background color. The change applies to that position in all nine circles and in the Layers indicator. Rules and digits stay the same. The game rejects very similar colors and adjusts text to black or white according to the background; still, choose a combination that is clear on your screen. Restore colors brings back the initial palette. Your chosen colors are saved in this browser.
Circle sum: an optional helper
Hover the mouse over Σ to see the sum of the digits currently placed in that circle, including its starting clues. Small Pencil notes do not count. The number shown beside Σ remains the fixed target sum, not the current total.
In Settings, turn off “Show current circle sum in tooltip” to calculate it yourself and increase the challenge. This preference is saved. The Σ target and rule checking still work. The helper uses the browser’s hover tooltip; touchscreens may not offer that same hover interaction.
Music, sound and silence
Every page load begins with Auto-mute on and Music and Sound unchecked. Turn off Auto-mute to unlock the controls, then choose Music, Sound or both. Music plays the electronic loop; Sound enables selection and error effects. Volume affects both music and effects.
Turning Auto-mute back on switches off and clears both channels. Hiding the tab silences audio. If the browser requires an interaction to play it, a click or tap lets it retry. Your colors persist between visits; audio starts muted on each page load.
Expand requests full screen when the browser supports it. Choosing colors or changing levels before PLAY does not start the timer. Restart discards the current game and prepares another at the same level, with the timer at 00:00 until PLAY. A started game requires confirmation.
HINT: a boost when you get stuck
One revealed cell can unlock several deductions. If you have been stuck for a while, Hint lets you discover the correct digit in an empty cell you choose, then keep solving the rest yourself. It is optional: you can complete a game without using it.
Once the game has started, select an empty cell and press Hint. The offer shows which cell will be revealed. You can cancel without changing the board. In rewarded-video mode, the cell is revealed only after the reward is received for completing the video; if unavailable or the sequence is canceled, the hint is not applied.
The website currently uses a demonstration of this sequence; it does not yet show real rewarded ads. The revealed cell is marked on the board, updates Layers and rows/columns, and removes that digit from related notes. Undo can reverse the hint.
To make the most of it, first consider where it gives you the most information. A center cell participates in four groups; another cell may complete a layer with only one digit remaining. After the reveal, revisit its sum and candidates: the benefit can be a chain of moves, not just one more digit.