     Sudoku Solution Path   Copyright © Kevin Stone R4C9 can only be <2> R6C4 can only be <9> R5C7 can only be <6> R5C8 can only be <3> R6C9 can only be <7> R6C6 can only be <8> R4C4 can only be <4> R6C1 can only be <6> R5C5 can only be <2> R4C6 can only be <1> R1C4 can only be <7> R4C1 can only be <9> R9C4 can only be <2> R1C9 is the only square in row 1 that can be <3> R1C8 is the only square in row 1 that can be <6> R8C8 can only be <9> R8C5 can only be <7> R7C7 can only be <1> R9C7 can only be <7> R8C9 can only be <6> R2C1 is the only square in row 2 that can be <7> R9C1 is the only square in row 9 that can be <3> R9C3 is the only square in row 9 that can be <6> R9C9 is the only square in row 9 that can be <5> R2C9 is the only square in column 9 that can be <1> Intersection of row 1 with block 1. The values <18> only appears in one or more of squares R1C1, R1C2 and R1C3 of row 1. These squares are the ones that intersect with block 1. Thus, the other (non-intersecting) squares of block 1 cannot contain these values.    R2C2 - removing <8> from <489> leaving <49>    R3C1 - removing <8> from <258> leaving <25>    R3C3 - removing <8> from <589> leaving <59> Squares R3C1<25>, R3C3<59> and R3C7<29> in row 3 form a comprehensive locked triplet. These 3 squares can only contain the 3 possibilities <259>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the row.    R3C5 - removing <9> from <489> leaving <48> Squares R3C5 and R3C9 in row 3 and R7C5 and R7C9 in row 7 form a Simple X-Wing pattern on possibility <4>. All other instances of this possibility in columns 5 and 9 can be removed.    R2C5 - removing <4> from <489> leaving <89> Squares R5C2, R5C3, R1C2 and R1C3 form a Type-3 Unique Rectangle on <18>. Upon close inspection, it is clear that: (R1C2 or R1C3)<249>, R3C3<59>, R3C1<25> and R2C2<49> form a locked quad on <2459> in block 1. No other squares in the block can contain these possibilities    R1C1 - removing <2> from <128> leaving <18> Squares R2C2 (XY), R2C8 (XZ) and R9C2 (YZ) form an XY-Wing pattern on <8>. All squares that are buddies of both the XZ and YZ squares cannot be <8>.    R9C8 - removing <8> from <48> leaving <4> R9C6 can only be <9> R2C8 can only be <8> R7C9 can only be <8> R2C5 can only be <9> R3C9 can only be <4> R3C5 can only be <8> R7C1 can only be <5> R9C2 can only be <8> R1C6 can only be <4> R7C5 can only be <4> R2C2 can only be <4> R7C3 can only be <9> R3C1 can only be <2> R3C3 can only be <5> R5C2 can only be <1> R3C7 can only be <9> R8C1 can only be <1> R1C7 can only be <2> R5C3 can only be <8> R1C2 can only be <9> R8C2 can only be <2> R1C3 can only be <1> R1C1 can only be <8> [Puzzle Code = Sudoku-20190416-SuperHard-071585]    