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