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