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Hi,

A Just For Fun Killer, to keep you busy waiting for the next Ed's Assassin.

This puzzle is not planned to be submitted for a further Assassin. I would say it is quite particular : you have to find the "key-move"
to open it ! SSolver uses trial and error moves to find the first digit
that enables to open the puzzle, but there is a logical argument
to find it. SScore is 2.21, but if you find this logcal argument,
that score becomes around 1.5 (sscore). Try it, I had fun to solve it.

[edit to add new image - Ed]


PS code :
3x3::k:5888:2049:2306:2306:7428:7428:5126:5126:5126:5888:2049:2049:7428:7428:3598:3599:3599:2833:5888:2835:10516:10516:7428:3598:3599:3599:2833:5888:2835:2589:10516:7428:3360:3360:2338:2338:4388:4388:2589:10516:3880:3880:3360:2338:5164:6701:4388:6701:10516:4913:4913:4913:4913:5164:6701:6701:6701:10516:10516:3131:3131:3901:5164:1599:6464:6464:10516:3395:3395:3131:3901:3901:1599:6464:6464:6464:3404:3404:3150:3150:3150:

Welcome manu! Great to have a keen new puzzle maker. No way can I get through 4 puzzles in a week though! Please spread them out more!hmmm...enjoyed the start! Spent way too much time on this one - enough for a 1.75 puzzle.

Not sure what I'm missing but this is where I'm up to. Afmob has offered to give me a hint so posting progress here in case others are interested.



Cheers
Ed

You've almost made it to the finishing line! There is a cage blocker (build by two cells) in C2 which helps to eliminate some combos from a cage and more importantly two candidates from that cage which is enough to finally open up this Killer.

Spot on! Thanks Afmob! Still took me a few minutes to find the one you were talking about. At least it wasn't something simple. The rest was easy.

I'll edit in a walkthrough and a rating. Altering the code to give SS the first placement gives it a score of 1.74 which sounds very much the way I found this one.

Thanks for a really challenging puzzle manu!

Cheers
Ed

Decided to make this WT a new post. This is such a good puzzle it deserves to be back at the top. Actually, it's a shame it's not one of the official Assassins. It's perfect for a really tough A. To me, feels like a classic 1.5 rating with lots of thoughtful work (step 2, 4, 18 and of course 27) and just one tedious section (steps 12 & 15). Really liked this one manu after I thought of it as JFFC (Just For a Frightful Challenge) . Thanks a lot!

Please let me know of any corrections or clarifications [edit to step 4: thanks Afmob; and some typos: thanks manu].

JFFKiller 1
Prelims
i. 8(3)n1: no 6,7,8,9
ii. 9(2)n1: no 9
iii. 11(2)n1: no 1
iv. 41(8)n1: no 4
v. 14(2)n2 = {59/68}
vi. 20(3)n3: no 1,2
vii. 14(4)n3: no 9
viii. 11(2)n3: no 1
ix. 10(2)n4: no 5
x. 15(2)n5 = {69/78}
xi. 9(3)n6: no 7,8,9
xii. 20(3)n6: no 1,2
xiii. 6(2)n7 = {15/24}
xiv. 2 of 13(2) cages in n8: no 1,2,3

1. "45" c1234: 1 outie r7c5 + 4 = 1 innie r2c4
1a. r7c5 = 1,2.3,5
1b. r2c4 = 5,6,7,9

2. r7c5 "see" all cells in c4 either directly (through the same 41(8)n1 cage or n8) or indirectly though i/o c1234 (step 1) EXCEPT r1c4
2a. since r2c4 cannot equal r7c5 (step 1) -> r1c4 = r7c5 = (1235)
2b. r9c4 = 4 (hsingle c4)
2c. no 2 r8c1

3. The 2 13(2) cages in n8 = {58/67}: all 4 candidates locked for n8

4. r89c56 must have both of (68)
4a. 15(2)n6 = {69/78} must have one of (68)
4b. which leaves only one spot left for (68) in c56 -> {68} blocked from 14(2)n2

5. 14(2)n2 = {59}: both locked for n2 & c6
5a. no 6 in r5c5
5b. no 1 in r7c5 (i/o c1234 = -4 step 1)
5c. no 1 in r1c4 (step 2a)
5d. r1c3 = (67)

6. 5 in n8 only in c5: locked for c5

7. 5 in n8 only in 1 of the 2 13(2) cages: Locked Cages -> one of r89c6 must have 8
7a. 8 locked for n8 & c6
7b. no 7 in r5c5

8. 9 in n8 only in r78c4: 9 locked for 41(8)n1

9. "45" n147: 2 remaining innies r13c3 = 13 = {67}: both locked for c3 & n1
9a. no 4,5 r4c2
9b. no 3,4 in 10(2)n4

10. "45" r9: 2 outies r8c23 - 5 = 1 innie r9c1
10a. -> no 5 in r8c23 (since the innie & outie are in the same house, the 3rd cell can't be equal to the i/o diff: IOU)

11. "45" r9: 3 innies r9c123 = 16 = {169/259/358}(no 7) ({178/268} blocked by 13(2)n8; {367} has no candidate in r9c1)
11a. = [1/2/8, 2/3/6...]

12. "45" r9: 3 outies r8c123 = 11 = {137/146}(no 2,5,8,9) ({128/236} blocked by h16(3)r9 step 11a; {245} blocked by 4,5 only in r8c1)
12a. 1 locked for r8 & n7
12b. 6 & 7 only in r8c2 = (67)
12c. = [173/461]

13. 13(2)r8c5 = [58] since {67} is blocked by r8c2

14. {67} naked pair at r9c56: both locked for r9
14a. {67} naked pair at r59c6: both locked for c6

15. split cage 21(4)r89c23 must have r8c23 = [73/61] from step 12c = 10/7
15a. -> r9c23 = 11/14 = {29}/{59} = (259)
15b. naked triple {259} in r9c123: all locked for r9 & n7

16. naked triple {138} in r9c789: all locked for n9

17. "45" n9: 1 outie r7c6 + 6 = r7c9 = [17/39] = [3/7..]
17a. r7c6 = (13), r7c9 = (79)

18. "45" n7: 3 remaining innies r7c123 = 18 and must have 8 for n7 = {468} ({378} blocked by r7c69 step 17; missed this first time through, helps!)
18a. 4 & 6 locked for n7 & r7 & 26(5)n4. 8 also locked for 26(5)n4.

19. r8c123 = [173]
19a. no 4 in r3c2
19b. r9c1 = 5

20. Killer pair (29) in c3 in 10(2)n4 and r9c3: both locked for c3

21. "45" n7: 2 remaining outies r6c13 = 8 = [71/35]
21a. r6c1 = (37)

22. 23(4)n1 = {2489} ({2678} has 6,7 only in r4c1; {3479} blocked by r6c1)
22a. All locked for c1

23. r7c1 = 6

24. naked pair {37} in r56c1: 3 locked for n4
24a. no 8 in r3c2

25. 8 in n1 only in c1: locked for c1

26. "45" n47: 1 innie r4c1 + 1 = 1 remaining outie r3c2
26a. r4c1 = (24), r3c2 = (35)
26b. r4c2 = (68)

Now at the spot I was stuck.
27. 17(3)n4 must have 3/7 = {179/278/359}(no 4,6) ({368} blocked by r4c2; {467}=[7]{46} blocked by r47c2 = [4/6..])

Now it's cracked.
28. r4c1 = 4 (hsingle n4)
28a. r123c1 = {289}: 2 locked for n1

29. 8(3)n1 = {134}: locked for n1
29a. r34c2 = [56]
29b. r6c3 = 5 (hsingle n4)
29c. r6c1 = 3 (1 remaining outie n7)
29d. r5c1 = 7
29e. r5c56 = [96]
29f. no 1 in r4c3

Now trying to get it to singles ASAP
30. "45" n69: 4 outies r467c6 + r6c5 = 10 and must have 4 for n5
30a. r6c56 must have 4 -> other 3 cells in outies = 6 (no 7,8)
30b. 4 locked for r6
30c. must have 3 to reach 10 in 4 outies: 3 locked for c6

31. r6c56 = 4[1/2] = 5/6 -> r6c78 = 14/13 = {68/67}
31a. 6 locked for r6

32. deleted

33. 9(3)n6 = {135/234}: 3 locked for n6
33a. = [4/5..]

34. 20(3)n6 = {479/578}: 7 locked for c9
34a. = [4/5] -> r5c9 = (45)
34b. no 4 in 11(2)n3

35. Killer Pair (45) in n6 in 9(3) (step 33a) and r5c9: both locked for n6

36. 13(3)n5 = {139/238}(no 7)
36a. r4c6 = 3
36b. r7c6 = 1 -> r7c9 = 7 (1 remaining innie n9)

37. r5c8 = 3 (hsingle n6)
37a. r4c89 = {15}: both locked for r4 & n6

38. r56c9 = [49] (cage sum)
38a. no 2 in 11(2)n3

39. r45c7 = {28}: both locked for c7 & n6
39a. r78c7 = 11 = [56]

40. 2 remaining outies n6 r6c56 = 6 = {24}: 2 locked for r6 & n5

41. r56c2 = 10 = [28]

42. r23c6 = [59]
42a. 11(2)n3 = {38}: both locked for n3 & c9

43. 20(3)n3 = {569} ({479} blocked by r1c9 = (56)}
43a. all locked for r1 & n3
43b. r1c34 = [72]

Rest is singles

You found some really nice moves! Especially step 2 and 4 were very clever. I added a part of my wt which takes a longer (more standard but technical easier?) way to reach the first placement.

Alternative for Ed's step 2:

What an optimized walkthrough Ed! You have found beautifull moves and have managed to avoid combos contradiction chains.

Happy that you have liked this puzzle guys ! This encourages me to continue in making and improving puzzles !

PS: Here is what I had planned about the placement of the first digit while making this puzzle :

I did several steps before I ground to a halt. Then a comment made to me by Manu about Just For Fun 3 made me wonder whether a similar step could be used in this puzzle. It is probably essential to solve this puzzle without extreme difficulty, whereas for Just For Fun 3 it only made the solution slightly shorter while, at the same time, increasing the rating of any walkthrough that used it.

After that the fun returned to this puzzle although I did get stuck later, taking some time to find the important combination elimination in step 20.

I'll rate JFFK1 at 1.5 to Hard 1.5 the way I solved it; it's hard to know what rating to give the first step which is the technically hardest one. Afmob's alternative start using more standard steps may be technically slightly easier so the rating for this puzzle should probably be 1.5.

Here is my walkthrough. I started again with the key breakthrough step before using some of my previous steps.

Prelims

a) R1C34 = {18/27/36/45}, no 9
b) R23C6 = {59/68}
c) R23C9 = {29/38/47/56}, no 1
d) R34C2 = {29/38/47/56}, no 1
e) R45C3 = {19/28/37/46}, no 5
f) R5C56 = {69/78}
g) R89C1 = {15/24}
h) R8C56 = {49/58/67}, no 1,2,3
i) R9C56 = {49/58/67}, no 1,2,3
j) 8(3) cage in N1 = {125/134}, 1 locked for N1, clean-up: no 8 in R1C4
k) R1C789 = {389/479/569/578}, no 1,2
l) 9(3) cage in N6 = {126/135/234}, no 7,8,9
m) R567C9 = {389/479/569/578}, no 1,2
n) 14(4) cage in N3 = {1238/1247/1256/1346/2345}, no 9
o) 41(8) cage at R3C3 = {12356789}, no 4

1. 45 rule on C123 2 outies R19C4 = 1 innie R3C3 (I had this part before)
1a. R9C4 “sees” all cells of 41(8) cage at R3C3 except for R3C3, R9C4 not equal to R3C3 (because R19C4 = R3C3) -> R9C4 not equal to any cell in 41(8) cage -> R9C4 = 4, clean-up: no 5 in R1C3, no 2 in R8C1, no 9 in R8C56, no 9 in R9C56
1b. R19C4 = R3C3 -> R3C3 = R1C4 + 4, no 6,7 in R1C4, no 2,3,8 in R3C3, clean-up: no 2,3 in R1C3

2. Naked quad {5678} in R89C56, locked for N8
2a. Naked quint {56789} in R23589C6, locked for C6
2b. 9 in N8 locked in R7C45 + R8C4, locked for 41(8) cage at R3C3, clean-up: no 5 in R1C4 (step 1b), no 4 in R1C3

3. 45 rule on C1234 1 innie R2C4 = 1 outie R7C5 + 4, R2C4 = {567}, no 9 in R7C5

4. 45 rule on N7 2 remaining outies R6C13 = 8 = {17/26/35}, no 4,8,9
4a. R6C13 = 8 -> R7C123 = 18

5. 45 rule on N9 1 innie R7C9 = 1 outie R7C6 + 6 -> R7C9 = {789}

6. 45 rule on R9 3 outies R8C123 = 11 = {128/137/146} (cannot be {236} because R8C1 only contains 1,4,5, cannot be {245} which clashes with R89C1 because no 4 in R8C23), no 5,9, 1 locked for R8 and N7
6a. 1 in R9 locked in R9C789, locked for N9
6b. R9C789 = {129/138/156}, no 7

7. 45 rule on R9 3 remaining innies R9C123 = 16 = {259/268/358} (cannot be {367} because R9C1 only contains 2,5), no 7
7a. 7 in R9 locked in R9C56 = {67}, locked for R9 and N8, clean-up: no 5 in R9C789 (step 6b)
7b. Naked pair {58} in R8C56, locked for R8, clean-up: no 2 in R8C23 (step 6)
7c. 5 in R9 locked in R9C123, locked for N7

8. Killer pair 5,8 in R23C6 and R8C6, locked for C6, clean-up: no 7 in R5C5

9. 1 in C9 locked in R49C9
9a. 45 rule on N9 4 innies R1489C9 = 14 = {1238/1247/1256/1346}, no 9

10. 45 rule on C789 4(3+1) outies R467C6 + R6C5 = 10
10a. R1467C6 = {1234} = 10 -> R1C6 = R6C5 -> R467C6 + R6C5 = {1234}, 4 locked for N5
10b. R6C5678 cannot contain more than two of 1,2,3,4 -> no 1,2,3,4 in R6C78

11. 25(4) cage at R8C2 = {14569/23479} (cannot be {13489} because R9C123 only contains one of 8,9 (step 7), cannot be {14578} which clashes with combinations for R8C123 and R9C123, cannot be {24568} because 2,5,8 only in R9C23, cannot be {34567} because R8C123 cannot contain both of 6,7), no 8
11a. 8 in R9 locked in R9C789, locked for N9, clean-up: no 2 in R7C6 (step 5)
11b. R9C789 (step 6b) = {138} (only remaining combination), locked for R9 and N9
11c. Naked triple {259} in R9C123, locked for N7
11d. 2 in N8 locked in R7C45 + R8C4, locked for 41(8) cage at R3C3
11e. 2 in R467C6 + R6C5 (step 10a) locked in R46C6 + R6C5, locked for N5

12. R7C123 = 18 (step 4a) = {378/468}
12a. R7C123 = {378} => R7C9 = 9 => R7C6 = 3 (step 5) clashes with R7C123 -> no {378} in R7C123
12b. R7C123 = {468}, locked for R7, N7 and 26(5) cage at R6C1 -> R8C1 = 1, R9C1 = 5, clean-up: no 2 in R6C1, no 2,3,7 in R6C3
12c. Naked pair {37} in R8C23, locked for R8
[I originally saw step 12a as that chain but later saw the simpler
R7C69 = [17/39] (using step 5)
R7C123 = {468} (cannot be {378} which clashes with R7C69)]

13. R34C2 = {38/47/56} (cannot be {29} which clashes with R9C2), no 2,9
13a. 9 in N1 locked in R123C1, locked for C1

14. 45 rule on C1 3 innies R567C1 = 16 = {367} (only remaining combination, cannot be {268} because R6C1 only contains 3,7) -> R7C1 = 6, R56C1 = {37}, locked for C1 and N4, clean-up: no 4,8 in R3C2

15. 45 rule on N47 2 remaining innies R4C12 = 10 = [28/46], clean-up: no 6,7 in R3C2

16. R13C3 = {67} (hidden pair in N1), locked for C3 -> R8C23 = [73], clean-up: no 1 in R1C4, no 4 in R45C3
[Alternatively, which I spotted first, killer pair 3,5 in 8(3) cage and R3C2, locked for N1]
16a. Killer pair 2,9 in R45C3 and R9C3, locked for C3
16b. 1 in C4 locked in R34567C4, locked for 41(8) cage at R3C3, clean-up: no 5 in R2C4 (step 3)

17. 45 rule on R6 3 remaining innies R6C249 = 18 = {189/279/369/459/468} (cannot be {378} which clashes with R6C1, cannot be {567} which clashes with R6C13)
17a. 5 of {459} must be in R6C4 -> no 5 in R6C29
17b. {279} must be [279] -> no 7 in R6C9

18. R567C9 = {389/479/569/578}
18a. 5 of {569} must be in R5C9 -> no 6 in R5C9

19. 1 in R1 locked in R1C256
19a. 45 rule on R1 4 innies R1C1256 = 16 = {1249/1258/1348/1456} (cannot be {1267} which clashes with R1C3, cannot be {1357} which clashes with R1C34), no 7

20. 17(3) cage in N4 = {179/278/359} (cannot be {269/458} because R5C1 only contains 3,7, cannot be {368} which clashes with R4C2, cannot be {467} which clashes with R47C2), no 4,6

21. R4C12 = [46] (hidden pair in N4), R3C2 = 5, clean-up: no 9 in R2C6, no 6 in R2C9
21a. Naked triple {289} in R123C1, locked for N1

22. Naked quad {1289} in R45C3 + R56C2, locked for N4 -> R6C3 = 5, R6C1 = 3 (step 4), R5C1 = 7, clean-up: no 3 in R1C6 (step 10a), no 8 in R5C5
[R6C3 is a hidden single but the naked quad was easier to see]
22a. Naked pair {69} in R5C56, locked for R5 and N5, clean-up: no 1 in R4C3
22b. R5C1 = 7 -> R56C2 = 10 = [19/28/82], no 1 in R6C2
22c. 1 in N4 locked in R5C23, locked for R5
22d. 1 in R6 locked in R6C456, locked for N5

23. R9C6 = 7 (hidden single in C6), R9C5 = 6, R5C56 = [96], clean-up: no 8 in R23C6
23a. R23C6 = [59], R8C56 = [58], clean-up: no 2 in R2C9, no 6 in R3C9

24. 29(6) cage at R1C5 = {134678} (only remaining combination), no 2
24a. R1C4 = 2 (hidden single in N2), R1C3 = 7, R3C3 = 6, R8C4 = 9, R2C4 = 6 (hidden single in C4), R7C5 = 2 (hidden single in N8)

25. 4 in N5 locked in R6C56, locked for R6
25a. R6C5678 = {1468/2467}, no 9, 6 locked in R6C78, locked for R6

26. 9(3) cage in N6 = {135/234}, 3 locked for N6

27. R567C9 = {479/578} -> R7C9 = 7, R7C6 = 1 (step 5), R7C4 = 3, R1C6 = 4, R6C6 = 2, R4C6 = 3, R6C5 = 4 (step 10a), clean-up: no 4 in R23C9

28. Naked pair {89} in R6C29, locked for R6
28a. R6C4 = 1 (hidden single in R6)

29. R5C8 = 3 (hidden single in N6), clean-up: no 2 in R4C89 (step 26)
29a. Naked pair {15} in R4C89, locked for R4 and N6, clean-up: no 8 in R45C9 (step 27)
29b. R56C9 = [49], R6C2 = 8, R5C2 = 2 (step 22b), R45C3 = [91], R2C3 = 4, R5C7 = 8, R5C4 = 5, R7C23 = [48], R9C23 = [92], clean-up: no 2 in R3C9

30. Naked pair {38} in R23C9, locked for C9 and N3 -> R9C9 = 1, R9C78 = [38], R4C89 = [15], R1C9 = 6, R8C9 = 2

31. Naked pair {59} in R1C78, locked for R1 -> R1C1 = 8, R23C1 = [92]

32. R4C7 = 2 (hidden single in R4), R2C8 = 2 (hidden single in R2)

33. 45 rule on N9 2 remaining innies R78C7 = 11 = [56]

and the rest is naked singles