Gem Finder: Three Gems, One Blank
Read the puzzle
In a 6x6 grid, each number counts the gems in the 8 tiles around it, diagonals included; numbered tiles hold none. Rows from the top, dash for a plain tile: 1 - 0 1 1 1 / - 1 1 - - - / - 2 1 - 2 1 / C - 3 2 D 0 / 3 B - - - 1 / - - 3 - A 1. Three of the lettered tiles A, B, C, D hold a gem. Which lettered tile has no gem?
A number counts the gems in the 8 tiles around it; numbered tiles have none. Which lettered tile has NO gem?
Check every number around the lettered tiles.
D
D touches a 0, so it is empty; the numbers force gems under A, B and C.
How to solve it
Start with the zeros: every tile touching a 0 is empty. D, in row 4, column 5, touches the 0 at the end of that row, so D is empty. That 0 also clears row 5, column 5.
Now confirm the others. The bottom-right 1 touches only a 1, that cleared tile and A, so A has a gem.
For C, use the 0 in the top row: it clears row 1, column 2 and row 2, column 4. The top-left 1 then forces a gem in row 2, column 1. The 1 in row 2, column 3 is left with only row 3, column 4, so that tile has a gem too. The 1s in row 2, column 2 and row 3, column 3 are now full, which clears row 3, column 1 and row 4, column 2. The 2 in row 3, column 2 then has one gem and only C left, so C holds a gem.
For B, the 2 in row 4, column 4 already has the gem in row 3, column 4 and needs exactly one more from row 5, columns 3 and 4. The 3 in row 4, column 3 counts those two gems, so its third must be B.
So A, B and C hide gems, and D is the only empty tile.
