... by: Tomas

osiguy, can you elaborate:

Round 4
forcingChain 1 elimination
R1C1: 5
Forcing Chain JIT from R1C1: eliminate contradicted | Removed: R1C1(5)

Can you show chains used, and logic of elimination using these chains?

... by: osiguy

Here is the solve up to move 12 where it solves itself!

17x lastRemaining
11x pointingPair (elim)
9x alsXZ (elim)
5x forcingChain (elim)
7x nakedPair (elim)
13x nakedSingle
23x hiddenSingle
2x claiming (elim)
1x emptyRectangle (elim)
1x alsXYWing (elim)
1x finnedXWing (elim)
5x fullHouse
63 total eliminations 58/58 placed in 36 rounds
✓ FULLY SOLVED —
Round 1
lastRemaining R1C4 = 8✓
Notes before: 5 8 9 → placed 8
8 can only go here in Box 2 — peers block all other spots
Round 2
pointingPair 2 eliminations
R1C3: 7 R2C3: 7
7 in Box 4 points along C3 — eliminates 2 | Removed: R1C3(7), R2C3(7)
pointingPair 2 eliminations
R2C9: 5 R3C9: 5
5 in Box 6 points along C9 — eliminates 2 | Removed: R2C9(5), R3C9(5)
pointingPair 3 eliminations
R5C4: 6 R5C5: 6 R5C6: 6
6 in Box 6 points along R5 — eliminates 3 | Removed: R5C4(6), R5C5(6), R5C6(6)
pointingPair 1 elimination
R7C9: 7
7 in Box 8 points along R7 — eliminates 1 | Removed: R7C9(7)
Round 3
alsXZ 1 elimination
R6C5: 9
ALS-XZ: RCC=2, eliminates 9 | Removed: R6C5(9)
Round 4
forcingChain 1 elimination
R1C1: 5
Forcing Chain JIT from R1C1: eliminate contradicted | Removed: R1C1(5)
Round 5
forcingChain 1 elimination
R7C2: 3
Forcing Chain from R1C1: eliminate from R7C2 | Removed: R7C2(3)
Round 6
pointingPair 2 eliminations
R9C8: 3 R9C9: 3
3 in Box 7 points along R9 — eliminates 2 | Removed: R9C8(3), R9C9(3)
Round 7
forcingChain 2 eliminations
R6C2: 2,8
Forcing Chain from R1C1: eliminate from R6C2 | Removed: R6C2(2), R6C2(8)
Round 8
forcingChain 1 elimination
R1C3: 2
Forcing Chain from R1C3: eliminate contradicted | Removed: R1C3(2)
Round 9
forcingChain 1 elimination
R1C5: 9
Forcing Chain JIT from R1C5: eliminate contradicted | Removed: R1C5(9)
Round 10
nakedPair 3 eliminations
R1C2: 3 R1C8: 3,5
Naked Pair {3,5} in R1 at R1C3,R1C5 — eliminates 3 candidates | Removed: R1C2(3), R1C8(3), R1C8(5)
pointingPair 2 eliminations
R3C1: 9 R3C2: 9
9 in Box 2 points along R3 — eliminates 2 | Removed: R3C1(9), R3C2(9)
nakedSingle R1C8 = 1✓
Notes before: 1 → placed 1
Elimination left only {1} → place 1
Round 11
lastRemaining R3C8 = 5✓
Notes before: 3 4 5 → placed 5
5 can only go here in Box 3 — peers block all other spots
hiddenSingle R7C8 = 3✓
Notes before: 3 4 6 → placed 3
3 has only one spot in C8 (cell had candidates {3,4,6})
Round 12
pointingPair 4 eliminations
R4C5: 5 R6C5: 5 R8C5: 5 R9C5: 5
5 in Box 2 points along C5 — eliminates 4 | Removed: R4C5(5), R6C5(5), R8C5(5), R9C5(5)
claiming 1 elimination
R9C3: 5
5 in R8 confined to Box 7 — eliminates 1 | Removed: R9C3(5)
claiming 2 eliminations
R4C6: 5 R6C6: 5
5 in C4 confined to Box 5 — eliminates 2 | Removed:

... by: BGH

All your solutions confirmed.
Most interesting:
2 @ J2 Solves for 2 in Blocks R3C1, R3C3, R1C3 & R1C1

... by: BGH

After basics 29.2
2 Step Solution (Pretty interesting double swordfish in 7’s)
7 @ B7 (Swordfish #1, solves for all 7’s in swordfish #1) 33.2
7 @ E4 (Swordfish #2, solves for all 7’s in swordfish #2) Solution

... by: Frans Goosens

#689

Combination 2-digits cells

B7=4 No solution, Undo calculation
B7=7 ( G6=7 ) Solved,

Total solving time is : 8 sec.
Number of logical steps is : 856

... by: Dieter

#689 - initially populated cells: 23 = 28,4 %
No solver used, solver = brain.
basics: %

Strategy: numbers 1,2,3,7,8 occur most frequently, combine two cells.
combinations of G2 = (1,2,3) and J2 = (2,3,8)
G2=1 & J2=2 solves.

... by: Yves

Two one cell solutions
J2=2 or J7=4