Hard Star Battle answer — December 21, 2025

Full written solution

Every deduction from the walkthrough above, in order. Each technique is explained in the Star Battle strategy guide.

1. Starting position — the grid is split into regions (bold outlines). Each row, column, and region needs exactly two stars, and no two stars may touch.
2. Blocking rule: a star here would touch every other open cell in its region, leaving no room for the region's second star (row 2, column 4).
3. Blocking rule: a star here would touch every other open cell in its region, leaving no room for the region's second star (row 3, column 4).
4. Three candidates with two adjacent: Isolated candidate must hold a star (row 2, column 3).
5. Mark 6 cells adjacent to stars as X (row 1, column 2).
6. Two-option rule: Cell adjacent to both candidates (row 2, column 6).
7. Two-option rule: Cell adjacent to both candidates (row 3, column 6).
8. Blocking rule: a star here would touch every other open cell in its region, leaving no room for the region's second star (row 2, column 8).
9. Blocking rule: a star here would touch every other open cell in its region, leaving no room for the region's second star (row 7, column 3).
10. Blocking rule: a star here would touch every other open cell in its region, leaving no room for the region's second star (row 7, column 4).
11. Three candidates with two adjacent: Isolated candidate must hold a star (row 8, column 4).
12. Mark 6 cells adjacent to stars as X (row 7, column 5).
13. Two-option rule: Cell adjacent to both candidates (row 5, column 3).
14. Two-option rule: Cell adjacent to both candidates (row 5, column 4).
15. Two last candidates (column 3): Eliminate 1 cell adjacent to both (row 5, column 2).
16. Two last candidates (column 4): Eliminate 1 cell adjacent to both (row 5, column 5).
17. Clump analysis (Region 4): candidate clumps can only just supply the remaining stars (row 6, column 1).
18. Clump analysis (Region 8): candidate clumps can only just supply the remaining stars (row 3, column 8).
19. Crowding (Region 1): a star here would leave too little room for its 2 remaining stars (row 6, column 6).
20. Crowding (Row 7): a star here would leave too little room for its 2 remaining stars (row 6, column 8).
21. Region confined to row: Eliminate other row candidates (row 1, column 8).
22. Crowding (Column 8): a star here would leave too little room for its 2 remaining stars (row 8, column 7).
23. Region confined to row: Eliminate other row candidates (row 1, column 9).
24. Three candidates with two adjacent: Isolated candidate must hold a star (row 2, column 7).
25. Mark 3 cells adjacent to stars as X (row 1, column 6).
26. Region completion: 2 stars needed, 2 candidates (row 1, column 1).
27. Mark 1 cell adjacent to stars as X (row 2, column 1).
28. Region completion: 1 star needed, 1 candidate (row 1, column 5).
29. Mark 1 cell adjacent to stars as X (row 2, column 5).
30. Region completion: 1 star needed, 1 candidate (row 3, column 5).
31. Mark 3 cells adjacent to stars as X (row 4, column 4).
32. Row 2 complete: Mark 1 remaining cell as X (row 2, column 9).
33. Region completion: 1 star needed, 1 candidate (row 3, column 9).
34. Mark 2 cells adjacent to stars as X (row 4, column 8).
35. Row 3 complete: Mark 1 remaining cell as X (row 3, column 1).
36. Column completion: 1 star needed, 1 candidate (row 6, column 4).
37. Mark 2 cells adjacent to stars as X (row 6, column 3).
38. Column completion: 1 star needed, 1 candidate (row 4, column 3).
39. Mark 1 cell adjacent to stars as X (row 4, column 2).
40. Three candidates with two adjacent: Isolated candidate must hold a star (row 5, column 8).
41. Mark 5 cells adjacent to stars as X (row 4, column 7).
42. Region completion: 1 star needed, 1 candidate (row 5, column 6).
43. Row completion: 1 star needed, 1 candidate (row 4, column 1).
44. Mark 1 cell adjacent to stars as X (row 5, column 1).
45. Row completion: 1 star needed, 1 candidate (row 6, column 2).
46. Mark 2 cells adjacent to stars as X (row 7, column 1).
47. Column 1 complete: Mark 2 remaining cells as X (row 8, column 1).
48. Three candidates in a row: Middle cell can't hold a star (row 7, column 8).
49. Row completion: 2 stars needed, 2 candidates (row 7, column 7).
50. Mark 1 cell adjacent to stars as X (row 8, column 6).
51. Row completion: 1 star needed, 1 candidate (row 7, column 9).
52. Row completion: 1 star needed, 1 candidate (row 8, column 2).
53. Mark 1 cell adjacent to stars as X (row 9, column 2).
54. Column completion: 1 star needed, 1 candidate (row 9, column 6).
55. Mark 1 cell adjacent to stars as X (row 9, column 7).
56. Column completion: 1 star needed, 1 candidate (row 9, column 8).
57. Mark 1 cell adjacent to stars as X (row 9, column 9).
58. Solved! Every row, column, and region has its two stars, none touching.