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