Hard Star Battle answer — April 25, 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 4).
3. Region completion: 2 stars needed, 2 candidates (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 6, column 4).
6. Mark 5 cells adjacent to stars as X (row 6, column 3).
7. Column 4 complete: Mark 4 remaining cells as X (row 1, column 4).
8. Clump analysis (Column 3): candidate clumps can only just supply the remaining stars (row 1, column 2).
9. Clump analysis (Column 2): candidate clumps can only just supply the remaining stars (row 4, column 1).
10. Clump analysis (Column 5): candidate clumps can only just supply the remaining stars (row 1, column 6).
11. Clump analysis (Column 6): candidate clumps can only just supply the remaining stars (row 4, column 7).
12. Clump analysis (Region 3): candidate clumps can only just supply the remaining stars (row 3, column 8).
13. Star claim: Region 2 must place a star in column 2; cells touching all its options are eliminated (row 5, column 1).
14. Clump analysis (Row 5): candidate clumps can only just supply the remaining stars (row 4, column 6).
15. Clump analysis (Row 5): each clump must supply its full share of stars (row 5, column 9).
16. Mark 4 cells adjacent to stars as X (row 4, column 8).
17. Row completion: 1 star needed, 1 candidate (row 4, column 2).
18. Mark 2 cells adjacent to stars as X (row 3, column 1).
19. Row completion: 1 star needed, 1 candidate (row 6, column 2).
20. Mark 2 cells adjacent to stars as X (row 7, column 1).
21. Region complete: Mark 1 remaining cell as X (row 2, column 3).
22. Three candidates with two adjacent: Isolated candidate must hold a star (row 1, column 3).
23. Two-option rule: Cell adjacent to both candidates (row 2, column 8).
24. Clump analysis (Row 3): candidate clumps can only just supply the remaining stars (row 2, column 7).
25. Region completion: 1 star needed, 1 candidate (row 3, column 9).
26. Row completion: 2 stars needed, 2 candidates (row 2, column 1).
27. Mark 1 cell adjacent to stars as X (row 1, column 1).
28. Row completion: 1 star needed, 1 candidate (row 2, column 5).
29. Mark 2 cells adjacent to stars as X (row 1, column 5).
30. Row completion: 1 star needed, 1 candidate (row 3, column 7).
31. Column completion: 2 stars needed, 2 candidates (row 5, column 6).
32. Mark 1 cell adjacent to stars as X (row 5, column 7).
33. Column completion: 1 star needed, 1 candidate (row 7, column 6).
34. Mark 3 cells adjacent to stars as X (row 7, column 7).
35. Region completion: 2 stars needed, 2 candidates (row 8, column 3).
36. Mark 1 cell adjacent to stars as X (row 9, column 3).
37. Region completion: 1 star needed, 1 candidate (row 9, column 7).
38. Mark 2 cells adjacent to stars as X (row 8, column 8).
39. Region completion: 1 star needed, 1 candidate (row 7, column 8).
40. Row completion: 1 star needed, 1 candidate (row 8, column 1).
41. Mark 1 cell adjacent to stars as X (row 9, column 1).
42. Region completion: 1 star needed, 1 candidate (row 9, column 5).
43. Column 7 complete: Mark 1 remaining cell as X (row 1, column 7).
44. Region completion: 1 star needed, 1 candidate (row 1, column 8).
45. Solved! Every row, column, and region has its two stars, none touching.