The full reasoning can be found below the Sudoku.
Dec 24 - Super Hard
Puzzle Copyright © Kevin Stone
Share link: https://www.brainbashers.com/
Reasoning
R5C5 can only be <4>
R6C5 can only be <3>
R4C5 can only be <6>
R3C5 can only be <9>
R7C5 can only be <2>
R3C6 can only be <6>
R3C4 can only be <1>
R1C6 can only be <3>
R7C6 can only be <7>
R7C4 can only be <6>
R5C6 can only be <5>
R1C4 can only be <4>
R5C4 can only be <7>
R9C6 can only be <9>
R9C4 can only be <5>
R1C1 is the only square in row 1 that can be <2>
R4C1 is the only square in row 4 that can be <5>
R3C1 can only be <7>
R3C9 can only be <5>
R1C2 is the only square in row 1 that can be <5>
R6C9 is the only square in row 6 that can be <1>
R6C1 is the only square in row 6 that can be <4>
R9C8 is the only square in row 9 that can be <2>
R9C9 is the only square in row 9 that can be <4>
Intersection of column 2 with block 7. The value <7> only appears in one or more of squares R7C2, R8C2 and R9C2 of column 2. These squares are the ones that intersect with block 7. Thus, the other (non-intersecting) squares of block 7 cannot contain this value.
R9C3 - removing <7> from <167> leaving <16>
Intersection of block 4 with column 3. The values <789> only appears in one or more of squares R4C3, R5C3 and R6C3 of block 4. These squares are the ones that intersect with column 3. Thus, the other (non-intersecting) squares of column 3 cannot contain these values.
R1C3 - removing <9> from <169> leaving <16>
Intersection of row 1 with block 3. The values <89> only appears in one or more of squares R1C7, R1C8 and R1C9 of row 1. These squares are the ones that intersect with block 3. Thus, the other (non-intersecting) squares of block 3 cannot contain these values.
R2C9 - removing <9> from <679> leaving <67>
Intersection of block 6 with column 7. The value <8> only appears in one or more of squares R4C7, R5C7 and R6C7 of block 6. These squares are the ones that intersect with column 7. Thus, the other (non-intersecting) squares of column 7 cannot contain this value.
R1C7 - removing <8> from <689> leaving <69>
Squares R2C1 and R2C9 in row 2 and R8C1 and R8C9 in row 8 form a Simple X-Wing pattern on possibility <6>. All other instances of this possibility in columns 1 and 9 can be removed.
R1C9 - removing <6> from <689> leaving <89>
R9C1 - removing <6> from <36> leaving <3>
R7C1 can only be <8>
R7C9 can only be <3>
R4C7 is the only square in row 4 that can be <3>
The puzzle can be reduced to a Bivalue Universal Grave (BUG) pattern, by making this reduction:
R8C9=<68>
These are called the BUG possibilities. In a BUG pattern, in each row, column and block, each unsolved possibility appears exactly twice. Such a pattern either has 0 or 2 solutions, so it cannot be part of a valid Sudoku
When a puzzle contains a BUG, and only one square in the puzzle has more than 2 possibilities, the only way to kill the BUG is to remove both of the BUG possibilities from the square, thus solving it
R8C9 - removing <68> from <678> leaving <7>
R8C2 can only be <9>
R8C8 can only be <8>
R2C9 can only be <6>
R4C9 can only be <9>
R9C7 can only be <6>
R9C3 can only be <1>
R1C7 can only be <9>
R1C9 can only be <8>
R5C7 can only be <8>
R1C8 can only be <1>
R2C1 can only be <9>
R4C3 can only be <7>
R5C3 can only be <9>
R6C7 can only be <7>
R6C3 can only be <8>
R8C1 can only be <6>
R2C2 can only be <1>
R9C2 can only be <7>
R1C3 can only be <6>
R2C8 can only be <7>
Today's Sudoku Puzzles
All daily items change at midnight GMT set time zone
Note: BrainBashers has a Dark Mode option. For BrainBashers, I'd recommend not using your browser's built-in dark mode, or any dark mode extensions (sometimes you can add an exception for a specific website).