There are four difficulties to choose from.
Here you can find UPDATED information regarding the required solving techniques for each difficulty. They are not identical to what I earlier posted for Samurai.
All four difficulties are variations of the same puzzle, i.e. they have identical solutions.
EDIT:
This time I personally found the Apprentice version a bit too easy, so in the future I will probably try to notch it up a bit, unless feedback tells me not to do so.
A) Novice.
B) Apprentice (mainstream edition).
C) Master.
D) Guru (I checked and chains only is possible, but fun?).
Regular Clueless Explosion #2A (Novice)
Rating based on required solving techniques: Easy
004002037002000004300409800009005600000007000750040000006000005000500300900300000
019008070000009801300500009000200000006800005005060308000970000000006004630000000
000090030000008400308420006050900070000100300009040100003804020000000005100000000
000007040805000000200039801600070034500204000900000000060005090000800002000010700
170208000000007204040000908000384060006000003700600050004050020005006000060000000
005060400000005700800400020010050090007806002086002007508600001000000000000000000
004009007000004000007020004900500070008002501100608000005001986000800000600000000
086010000900000800000600930020060009007005000004200507009800053400500700500070000
100043800504000200000005094002009100000800000805100040980000300006001000000000000
Regular Clueless Explosion #2B (Apprentice)
Rating based on required solving techniques: Barely Tough
My personal rating based on actual solving: Moderate
000002007002000004300009800009000600000007000750040000000000005000500300900300000
009008000000000801300500009000200000006000005005060308000900000000006004630000000
000090030000008000308420006050000070000100300009040100000804020000000005100000000
000007040805000000200039001000000034000204000900000000060005090000800002000010700
170200000000007000000000908000004060006000003700600050004050020005006000060000000
005060400000000700800400020010000090007806002006002000508600001000000000000000000
004009007000004000007020004900500000008002001100008000005001980000800000600000000
006010000900000800000600030020060009000005000004200500009000053000500700500070000
100043800500000200000005004002009000000800000805100040980000300006000000000000000
Regular Clueless Explosion #2C (Master)
Rating based on required solving techniques: Barely Extra Hard
000002007002000004300009800009000600000007000750040000000000005000500300900300000
009008000000000801300500009000200000006000005005060308000900000000000004630000000
000090030000008000308420006050000070000100300009040100000004020000000005100000000
000007040805000000200039001000000034000204000900000000060005000000800002000010700
170200000000007200000000908000004060000000003700600050004050020005006000060000000
005060400000000700800400020010000090007806002006002000508600001000000000000000000
004009007000004000007020004900500000008002001100008000005001980000800000600000000
006010000900000800000600030020060009000005000004200500009000053000000700500070000
100043800500000200000005004002009000000800000805100040980000300006000000000000000
Regular Clueless Explosion #2D (Guru)
Rating based on required solving techniques: Ultra Hard
000002007002000004300009800009000600000007000750040000000000005000500300900300000
009008000000700801300500009000200000000000005005060308000900000000006004630000000
000090030000008000308420006050000070000100300009040100000804020000000005100000000
000007040805000000200039001000000030000204000900000000060005090000800002000010700
170200000000007000000000908000004060000000003700600050004050020005006000060000000
005000400000000700800400020010000090007806002006002000508600001000000000000000000
004009007000004000007020004900500000008002001100008000005001980000800000600000000
006010000900000800000600030020060009000005000004200500009000003000500000500070000
100043800500000200000005004002009000000800000805100040980000300006000000000000000