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