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