Hard Star Battle answer — September 3, 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 3, column 9).
3. Three candidates with two adjacent: Isolated candidate must hold a star (row 4, column 9).
4. Mark 4 cells adjacent to stars as X (row 3, column 8).
5. Two-option rule: Cell adjacent to both candidates (row 1, column 8).
6. Two-option rule: Cell adjacent to both candidates (row 1, column 9).
7. 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 3).
8. Clump analysis (Row 9): candidate clumps can only just supply the remaining stars (row 6, column 4).
9. Clump analysis (Row 8): candidate clumps can only just supply the remaining stars (row 7, column 8).
10. Clump analysis (Row 8): each clump must supply its full share of stars (row 8, column 1).
11. Mark 3 cells adjacent to stars as X (row 7, column 1).
12. Row completion: 2 stars needed, 2 candidates (row 7, column 3).
13. Mark 2 cells adjacent to stars as X (row 6, column 2).
14. Region complete: Mark 2 remaining cells as X (row 5, column 1).
15. Row completion: 1 star needed, 1 candidate (row 7, column 5).
16. Mark 2 cells adjacent to stars as X (row 6, column 5).
17. Three candidates in a row: Middle cell can't hold a star (row 6, column 8).
18. Row completion: 2 stars needed, 2 candidates (row 6, column 7).
19. Mark 2 cells adjacent to stars as X (row 5, column 6).
20. Row completion: 1 star needed, 1 candidate (row 6, column 9).
21. Column completion: 2 stars needed, 2 candidates (row 2, column 8).
22. Mark 4 cells adjacent to stars as X (row 1, column 7).
23. Column completion: 1 star needed, 1 candidate (row 8, column 8).
24. Mark 2 cells adjacent to stars as X (row 8, column 9).
25. Region complete: Mark 1 remaining cell as X (row 4, column 6).
26. Column completion: 1 star needed, 1 candidate (row 4, column 7).
27. Mark 1 cell adjacent to stars as X (row 3, column 6).
28. Row 4 complete: Mark 4 remaining cells as X (row 4, column 1).
29. Region completion: 1 star needed, 1 candidate (row 5, column 5).
30. Mark 1 cell adjacent to stars as X (row 5, column 4).
31. Column 5 complete: Mark 4 remaining cells as X (row 1, column 5).
32. Three candidates with two adjacent: Isolated candidate must hold a star (row 9, column 6).
33. Three candidates with two adjacent: Isolated candidate must hold a star (row 1, column 4).
34. Mark 3 cells adjacent to stars as X (row 1, column 3).
35. Three candidates with two adjacent: Isolated candidate must hold a star (row 3, column 2).
36. Mark 4 cells adjacent to stars as X (row 2, column 1).
37. Row completion: 1 star needed, 1 candidate (row 2, column 6).
38. Mark 1 cell adjacent to stars as X (row 1, column 6).
39. Row completion: 1 star needed, 1 candidate (row 3, column 4).
40. Column completion: 1 star needed, 1 candidate (row 1, column 1).
41. Mark 1 cell adjacent to stars as X (row 1, column 2).
42. Column completion: 1 star needed, 1 candidate (row 5, column 2).
43. Mark 1 cell adjacent to stars as X (row 5, column 3).
44. Column completion: 1 star needed, 1 candidate (row 9, column 3).
45. Mark 1 cell adjacent to stars as X (row 9, column 4).
46. Solved! Every row, column, and region has its two stars, none touching.