Sudoku Puzzle © Kevin Stone

R6C5 can only be <9>

R6C8 can only be <5>

R4C5 can only be <1>

R8C5 can only be <6>

R9C5 can only be <7>

R1C5 can only be <4>

R2C5 can only be <8>

R2C7 can only be <7>

R2C6 can only be <3>

R1C7 can only be <9>

R9C7 can only be <3>

R2C4 can only be <6>

R5C6 can only be <2>

R5C4 can only be <3>

R2C9 can only be <1>

R3C4 can only be <9>

R3C6 can only be <7>

R1C2 is the only square in row 1 that can be <7>

R3C1 is the only square in row 3 that can be <3>

R3C2 is the only square in row 3 that can be <4>

R6C2 can only be <2>

R4C8 is the only square in row 4 that can be <3>

R7C2 is the only square in column 2 that can be <8>

R1C8 is the only square in column 8 that can be <2>

R1C3 can only be <6>

Squares R7C6 and R7C8 in row 7 form a simple locked pair. These 2 squares both contain the 2 possibilities <19>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the row.

R7C1 - removing <19> from <12459> leaving <245>

R7C9 - removing <9> from <459> leaving <45>

Squares R7C8 and R9C8 in column 8 form a simple locked pair. These 2 squares both contain the 2 possibilities <19>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the column.

R5C8 - removing <9> from <689> leaving <68>

Squares R7C8 and R9C8 in block 9 form a simple locked pair. These 2 squares both contain the 2 possibilities <19>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the block.

R8C9 - removing <9> from <4589> leaving <458>

Intersection of row 9 with block 7. The value <5> only appears in one or more of squares R9C1, R9C2 and R9C3 of row 9. These squares are the ones that intersect with block 7. Thus, the other (non-intersecting) squares of block 7 cannot contain this value.

R7C1 - removing <5> from <245> leaving <24>

R8C1 - removing <5> from <12459> leaving <1249>

R8C3 - removing <5> from <2459> leaving <249>

Squares R6C1 and R6C9 in row 6 and R7C1 and R7C9 in row 7 form a Simple X-Wing pattern on possibility <4>. All other instances of this possibility in columns 1 and 9 can be removed.

R5C1 - removing <4> from <1479> leaving <179>

R5C9 - removing <4> from <46789> leaving <6789>

R8C1 - removing <4> from <1249> leaving <129>

R8C9 - removing <4> from <458> leaving <58>

Squares R3C8, R3C9, R5C8 and R5C9 form a Type-1 Unique Rectangle on <68>.

R5C9 - removing <68> from <6789> leaving <79>

Squares R5C3 (XY), R6C1 (XZ) and R5C9 (YZ) form an XY-Wing pattern on <7>. All squares that are buddies of both the XZ and YZ squares cannot be <7>.

R5C1 - removing <7> from <179> leaving <19>

R6C9 - removing <7> from <47> leaving <4>

R6C1 can only be <7>

R7C9 can only be <5>

R5C7 can only be <8>

R7C4 can only be <2>

R8C9 can only be <8>

R8C7 can only be <4>

R3C9 can only be <6>

R3C8 can only be <8>

R4C9 can only be <9>

R4C1 can only be <5>

R5C9 can only be <7>

R5C8 can only be <6>

R5C2 can only be <1>

R7C1 can only be <4>

R8C4 can only be <5>

R4C2 can only be <6>

R2C1 can only be <2>

R5C1 can only be <9>

R9C2 can only be <5>

R9C3 can only be <9>

R9C8 can only be <1>

R5C3 can only be <4>

R8C3 can only be <2>

R7C8 can only be <9>

R2C3 can only be <5>

R8C1 can only be <1>

R7C6 can only be <1>

R8C6 can only be <9>