Singles

1. Shade duplicates. After shading, no number may appear twice among the white cells of a row or column. Not every number needs to remain in each row.

2. Separate black cells. Two black cells may touch at a corner, but never along an edge.

3. Connect all whites. Every white cell must be reachable from every other white cell by moving up, down, left or right through white cells.

Choose ■ Shade, ○ Keep or Clear, then tap cells. A circle is only a reminder to keep that cell white. Unmarked cells also count as white; you never need to circle every cell to finish. Clear removes either kind of mark. Undo retains the last 64 edits.

Try looking for two equal numbers separated by one cell: that middle cell must stay white. Shading a cell also keeps its edge-neighbours white. If a move cuts off white cells, clear it or Undo.

Keyboard: arrows select; B shades; W circles; U undoes; Delete clears; Enter applies the active tap mode. No timer or answer-revealing hint. Historical completion is separate from the current board.