Sudoku vs Kuromasu: Number Placement and Shading Logic Compared

Sudoku determines one symbol for every cell

Classic Sudoku uses a fixed 9x9 grid divided into rows, columns, and 3x3 boxes. Every one of those units must contain the nine symbols exactly once. Solving means narrowing each empty cell from several possible values to one. Shapedoku makes the structure more visual by replacing digits with a triangle, hexagon, circle, crystal, heart, diamond, square, crescent moon, and lotus flower. The shapes do not represent quantities, so the reasoning is pure placement logic. A shape is removed from a cell because that shape already appears in a peer or because a candidate pattern proves it must be used somewhere else. Notes help preserve several possibilities without guessing. The final board is completely filled, and the main global requirement is that every unit contains a complete non-repeating set.

Kuromasu uses numbers as visibility clues

Kuromasu, also known as Kurodoko, starts with number clues already placed on the grid. Those numbered cells remain white. Each clue tells you how many white cells are visible horizontally and vertically from that clue, counting the clue cell itself. Visibility continues through white cells and stops at a black cell or the edge of the grid. The other rules control the shading: black cells cannot share an edge, although they may touch diagonally, and all white cells must form one orthogonally connected area. A clue therefore describes the combined reach of four directions rather than a value to place in one cell. If making a distant cell white would cause a clue to see too many cells, a black blocker must appear before it. If a black cell is confirmed, each orthogonally adjacent cell must remain white because two black cells cannot touch. Connectivity can also force cells white when shading them would cut the remaining white area apart.

Compare candidate values with possible black boundaries

The puzzles feel different, but both reward careful bookkeeping. Sudoku asks whether a symbol can survive in a cell. Kuromasu asks whether a cell can still be black or must remain white while every clue's visibility total stays possible. Do not solve a clue by considering only one direction. Its number counts the clue itself plus the visible white cells in all four orthogonal directions, so a longer white run on one side leaves less visibility available on the others. Once a clue has enough confirmed visible cells to meet its total, the next cell beyond each required visible run may need to be black if extending visibility would exceed the clue. Always verify that this shading also respects the no-touch and connectivity rules. Choose Sudoku when you enjoy many candidate values and fixed units. Choose Kuromasu when you enjoy shading, line-of-sight counts, and global connectivity. If you want another dark, calm constraint puzzle after either one, Mystic Sort from SnailPixel uses glowing potion colors and careful pours to separate each color cleanly. Google Play: [https://play.google.com/store/apps/details?id=com.snailpixel.mysticsort](https://play.google.com/store/apps/details?id=com.snailpixel.mysticsort). Shapedoku remains a natural choice for classic Sudoku logic with a more visual board.

1. In Sudoku, eliminate symbol candidates using rows, columns, and boxes.
2. In Kuromasu, treat every undecided cell as a possible white cell or black blocker.
3. Remember that each Kuromasu clue counts itself and all visible white cells in four orthogonal directions.
4. After shading a black cell, keep its orthogonal neighbors white.
5. Check that all white cells can remain connected before committing to a black placement.
6. Choose Sudoku for value placement or Kuromasu for visibility, shading, and connectivity logic.