     Sudoku Solution Path   Copyright © Kevin Stone R1C5 can only be <7> R4C3 can only be <1> R6C3 can only be <4> R5C1 can only be <3> R5C4 can only be <4> R5C9 can only be <8> R7C4 can only be <3> R5C5 can only be <9> R5C6 can only be <1> R3C4 can only be <6> R9C5 can only be <8> R4C5 can only be <3> R7C6 can only be <4> R3C6 can only be <3> R4C4 can only be <7> R6C4 can only be <2> R6C6 can only be <6> R4C7 can only be <6> R6C5 can only be <5> R4C6 can only be <8> R6C7 can only be <3> R1C8 is the only square in row 1 that can be <9> R3C2 is the only square in row 3 that can be <5> R7C3 is the only square in row 7 that can be <9> R9C8 is the only square in row 9 that can be <2> R3C7 is the only square in row 3 that can be <2> R2C2 is the only square in row 2 that can be <2> R8C7 is the only square in column 7 that can be <4> Squares R3C8 and R7C8 in column 8 form a simple locked pair. These 2 squares both contain the 2 possibilities <78>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the column.    R2C8 - removing <78> from <3678> leaving <36>    R8C8 - removing <78> from <3678> leaving <36> Squares R8C8 and R9C9 in block 9 form a simple locked pair. These 2 squares both contain the 2 possibilities <36>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the block.    R8C9 - removing <36> from <1367> leaving <17> Intersection of column 2 with block 7. The values <37> 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 these values.    R8C3 - removing <7> from <678> leaving <68> Squares R1C1 and R1C9 in row 1 and R9C1 and R9C9 in row 9 form a Simple X-Wing pattern on possibility <6>. All other instances of this possibility in columns 1 and 9 can be removed.    R2C1 - removing <6> from <168> leaving <18>    R2C9 - removing <6> from <1367> leaving <137>    R8C1 - removing <6> from <168> leaving <18> Squares R2C1 and R2C7 in row 2 form a simple locked pair. These 2 squares both contain the 2 possibilities <18>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the row.    R2C3 - removing <8> from <678> leaving <67>    R2C9 - removing <1> from <137> leaving <37> Squares R2C1 and R8C1 in column 1 form a simple locked pair. These 2 squares both contain the 2 possibilities <18>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the column.    R1C1 - removing <1> from <146> leaving <46> Squares R7C7 and R8C1 form a remote locked pair. <18> can be removed from any square that is common to their groups.    R8C9 - removing <1> from <17> leaving <7>    R7C2 - removing <1> from <17> leaving <7> R7C8 can only be <8> R7C7 can only be <1> R3C8 can only be <7> R2C9 can only be <3> R2C8 can only be <6> R9C9 can only be <6> R3C3 can only be <8> R2C7 can only be <8> R9C1 can only be <4> R1C9 can only be <1> R8C8 can only be <3> R1C2 can only be <4> R2C1 can only be <1> R2C3 can only be <7> R8C3 can only be <6> R8C2 can only be <1> R9C2 can only be <3> R1C1 can only be <6> R8C1 can only be <8> [Puzzle Code = Sudoku-20191206-VeryHard-217998]    