Hard Star Battle answer — October 5, 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 4, column 2).
3. Three candidates with two adjacent: Isolated candidate must hold a star (row 4, column 3).
4. Mark 7 cells adjacent to stars as X (row 3, column 2).
5. 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 2).
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 2, column 2).
7. Three candidates with two adjacent: Isolated candidate must hold a star (row 2, column 3).
8. Mark 3 cells adjacent to stars as X (row 1, column 3).
9. Column 3 complete: Mark 4 remaining cells as X (row 6, column 3).
10. Clump analysis (Column 2): candidate clumps can only just supply the remaining stars (row 6, column 1).
11. Three candidates with two adjacent: Isolated candidate must hold a star (row 9, column 4).
12. Mark 3 cells adjacent to stars as X (row 8, column 4).
13. Two last candidates (column 4): Eliminate 2 cells adjacent to both (row 6, column 5).
14. Clump analysis (Column 5): candidate clumps can only just supply the remaining stars (row 2, column 6).
15. Clump analysis (Region 3): candidate clumps can only just supply the remaining stars (row 8, column 6).
16. Region completion: 1 star needed, 1 candidate (row 8, column 2).
17. Mark 1 cell adjacent to stars as X (row 7, column 2).
18. Column completion: 1 star needed, 1 candidate (row 6, column 2).
19. Mark 1 cell adjacent to stars as X (row 5, column 1).
20. Region completion: 1 star needed, 1 candidate (row 5, column 5).
21. Mark 4 cells adjacent to stars as X (row 4, column 5).
22. Column completion: 1 star needed, 1 candidate (row 7, column 4).
23. Three candidates with two adjacent: Isolated candidate must hold a star (row 7, column 6).
24. Mark 2 cells adjacent to stars as X (row 6, column 7).
25. Region completion: 1 star needed, 1 candidate (row 5, column 7).
26. Mark 4 cells adjacent to stars as X (row 4, column 7).
27. Row 5 complete: Mark 1 remaining cell as X (row 5, column 9).
28. Row completion: 1 star needed, 1 candidate (row 6, column 9).
29. Mark 2 cells adjacent to stars as X (row 7, column 8).
30. Region completion: 2 stars needed, 2 candidates (row 3, column 6).
31. Mark 4 cells adjacent to stars as X (row 2, column 5).
32. Region completion: 1 star needed, 1 candidate (row 3, column 8).
33. Mark 4 cells adjacent to stars as X (row 2, column 8).
34. Row completion: 1 star needed, 1 candidate (row 2, column 1).
35. Mark 2 cells adjacent to stars as X (row 1, column 1).
36. Region completion: 1 star needed, 1 candidate (row 4, column 1).
37. Column completion: 1 star needed, 1 candidate (row 1, column 5).
38. Mark 1 cell adjacent to stars as X (row 1, column 6).
39. Column 6 complete: Mark 1 remaining cell as X (row 9, column 6).
40. Region completion: 1 star needed, 1 candidate (row 9, column 7).
41. Mark 1 cell adjacent to stars as X (row 8, column 8).
42. Region completion: 1 star needed, 1 candidate (row 8, column 9).
43. Column 7 complete: Mark 1 remaining cell as X (row 1, column 7).
44. Column completion: 1 star needed, 1 candidate (row 1, column 8).
45. Mark 1 cell adjacent to stars as X (row 1, column 9).
46. Solved! Every row, column, and region has its two stars, none touching.