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