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