A shading puzzle. Shade cells so that no number repeats, unshaded, in any row or column — but never shade two cells that touch each other, even edge to edge.
Rules
Click a cell once to shade it, again to circle it (definitely keep), again to return it to normal.
Once solved, no unshaded number may repeat within any row or column.
No two shaded cells may be directly adjacent, horizontally or vertically.
A fresh grid is dealt each time you open or reset the page, so every attempt is a new puzzle.
Tips
If a number appears twice in the same row or column, at least one of the two copies must be shaded — start by finding those pairs before worrying about the rest of the grid.