Gem Finder: One Safe Tile
Read the puzzle
A 5 by 5 grid; a number counts gems in the 8 tiles around it (diagonals too), numbered tiles hold no gem, and # is a covered tile. Row 1: 1, 2, 2, #, #. Row 2: 2, A, #, #, 1. Row 3: 2, B, C, #, #. Row 4: 1, 2, #, 1, 0. Row 5: 0, 0, #, #, D. A, B, C and D are covered tiles. 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?
A 0 means none of the tiles around it has a gem.
D
D touches a 0, so it is empty. The numbers force gems under A, B and C.
How to solve it
Look for a 0 next to a lettered tile first. The 0 at the right end of row 4 touches D, which sits just below it. A 0 means none of the tiles around it hold a gem, so D is empty. That already answers the question, but check that the other three really do hide gems.
The 1 in the top-left corner touches only three tiles: the 2 to its right, the 2 below it and A. Numbers hold no gems, so A must be its one gem.
The 2 in row 2, column 1 touches A and B as its only covered tiles, so both hold gems: B has a gem.
The 0s in row 5 clear the covered tile in row 4, column 3 and the one in row 5, column 3. Then the 2 in row 4, column 2 touches only B and C as covered tiles that can hold gems. It needs 2, so C has a gem.
So A, B and C all hide gems, and D is the only safe tile.
The usual slip is picking C, because it sits further from the numbers on the left. But the 2 beside it forces a gem there.
Takeaway: a 0 is the quickest proof that a tile is safe.
Learn the method: Process of Elimination in Puzzles: Rule Out Until One Is Left
