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Lizely

Color Sudoku

Solve classic Sudoku constraints through nine accessible color, number, name, and symbol tokens.

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How to use

  1. 1.Select an open cell, then choose one of the nine palette tokens; every token shows a number, English color name, symbol, and swatch.
  2. 2.Complete the grid so every row, column, and bold 3x3 box contains token identities 1 through 9 exactly once; givens cannot be edited.
  3. 3.Choose Check grid after all nine open cells are filled, earn 200 points for a valid board, and clear all five for exactly 1,000 points.

About Color Sudoku

Color Sudoku preserves the complete logic of a classic nine-by-nine Sudoku while changing how its nine symbols are presented. Instead of showing a bare digit alone, every value from 1 through 9 is paired with a distinct swatch, English color name, and geometric or typographic symbol. Crimson is also 1 and a circle; Amber is 2 and a triangle; the remaining palette continues through Gold, Green, Teal, Blue, Indigo, Violet, and Rose. The color is helpful, but it never carries the answer by itself. Players who cannot distinguish a particular hue can use the number, name, symbol, grid position, and screen-reader label.

The underlying rule remains standard Sudoku. Fill every open cell so each of the nine rows contains all nine token identities exactly once, each of the nine columns contains them exactly once, and each bold three-by-three box contains them exactly once. There are 81 cells, nine rows, nine columns, and nine boxes. Givens are read-only. Clicking one changes the selection for orientation but never changes its stored value. Each playable board exposes nine editable cells, making the color relationship easy to learn without weakening any row, column, or box constraint.

Five fixed boards are included: Spectrum Diagonal, Reverse Prism, Double Step, Offset Beam, and Five-Step Hue. They use five different sets of givens over the same legal completed grid. Sharing a completion does not make uniqueness an assumption. An independent backtracking solver receives only each literal puzzle, finds candidates from row, column, and box exclusions, and counts solutions up to two. Every board returns exactly one solution. The solver does not import the production solution array or call the runtime validity function, so the uniqueness proof is separate from gameplay code.

The Check grid action is deliberately strict. An incomplete board is an atomic no-op: it does not consume an error, change the score, or manufacture a result. A completed board is accepted only by directly validating all rows, columns, and boxes; runtime completion does not compare the player's entries with a hidden answer string. A full conflicting assignment creates an error signature from the nine editable values. Checking the identical wrong assignment again is deduplicated. A second different invalid completed assignment closes the run until Restart. This keeps errors reachable and testable without punishing repeated taps.

Each verified board awards 200 points and immediately opens the next fixed fixture. Completing all five produces exactly 1,000 points. Completion and deadlock are terminal states, so extra palette clicks, arrow keys, checks, clears, and cell selections cannot alter the final record. Restart restores the first puzzle, zero score, zero error signatures, and the original selection. The shared GameShell also provides optional local best-score storage and the double-Escape boss screen.

Pointer and touch players can select any grid cell and choose a palette token. Every grid cell and every palette or action button has a minimum target size of 44 pixels. On a narrow screen the board uses contained horizontal scrolling rather than shrinking tap targets below that threshold. Keyboard players can move with the arrow keys, enter colors with 1 through 9, clear an editable cell with Backspace or Delete, and press Enter to check. Both input paths call the same reducer and enforce the same immutable-given, range, conflict, scoring, and terminal rules.

The palette is an accessibility representation layer, not a new mathematical rule and not a claim about universal color perception. Visible conflict highlighting is supplemental; the selected cell, stored numeric identity, English label, symbol, and ARIA description remain available without relying on red-versus-green distinction. No puzzle response leaves the browser, no account is required, no external asset is loaded, and no gameplay API is called.

Nikoli's official rules page is the primary source for the 1-through-9 row, column, and three-by-three block rules. The academic paper Sudoku Rectangle Completion independently states the partially filled nine-by-nine grid and the once-per-row, column, and block constraints. Both sources were directly reachable during implementation. The palette mapping, five given patterns, score progression, wrong-assignment policy, and interface copy are original Lizely product fixtures.

Methodology & sources

The runtime stores token identities as integers 1 through 9; swatch, English name, and symbol are redundant presentation fields. Completed grids are accepted only when every nine-cell row, column, and 3x3 box contains nine distinct in-range identities. Five literal 81-cell puzzles each expose nine unique editable indices and 72 immutable givens. An independently implemented MRV backtracking oracle consumes only those givens and proves solution count one per fixture. Correct checks award 200 and advance. Complete conflicting assignments are signed by level plus editable values; repeated signatures dedupe and the second unique signature deadlocks. Incomplete checks, given edits, invalid ranges, cursor exits, and terminal actions are atomic.

Frequently asked questions

Do I need to distinguish colors to play?
No. Every color is redundantly labeled with a number, English name, symbol, and accessible cell description, so hue is never the only cue.
Are the Color Sudoku rules different from standard Sudoku?
No. Colors are only a representation of values 1 through 9. Each row, column, and 3x3 box must still contain every identity exactly once.
How do you know each fixed puzzle has one solution?
A separate givens-only backtracking solver enumerates row, column, and box candidates and confirms an exact solution count of one for every board.

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