Hard Star Battle answer — October 12, 2026

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 9, column 6).
3. Blocking rule: a star here would touch every other open cell in its region, leaving no room for the region's second star (row 10, column 6).
4. Three candidates with two adjacent: Isolated candidate must hold a star (row 9, column 7).
5. Mark 6 cells adjacent to stars as X (row 8, column 6).
6. Two-option rule: Cell adjacent to both candidates (row 9, column 4).
7. Two-option rule: Cell adjacent to both candidates (row 10, column 4).
8. 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).
9. 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).
10. Three candidates with two adjacent: Isolated candidate must hold a star (row 5, column 8).
11. Mark 6 cells adjacent to stars as X (row 4, column 7).
12. Three candidates with two adjacent: Isolated candidate must hold a star (row 5, column 10).
13. Mark 2 cells adjacent to stars as X (row 4, column 10).
14. Row 5 complete: Mark 6 remaining cells as X (row 5, column 1).
15. Two-option rule: Cell adjacent to both candidates (row 2, column 7).
16. Two-option rule: Cell adjacent to both candidates (row 2, column 8).
17. Two-option rule: Cell adjacent to both candidates (row 8, column 9).
18. Clump analysis (Region 7): candidate clumps can only just supply the remaining stars (row 7, column 2).
19. Lookahead: Placing star here leads to contradiction - columns 7-10 can only hold 8 stars but the regions there would be forced to place 9 (row 1, column 6).
20. Crowding (Column 6): a star here would leave too little room for its 2 remaining stars (row 3, column 5).
21. Region completion: 1 star needed, 1 candidate (row 3, column 8).
22. Mark 2 cells adjacent to stars as X (row 2, column 9).
23. Column 8 complete: Mark 2 remaining cells as X (row 1, column 8).
24. Region completion: 1 star needed, 1 candidate (row 7, column 9).
25. Mark 2 cells adjacent to stars as X (row 7, column 10).
26. Clump analysis (Row 8): candidate clumps can only just supply the remaining stars (row 7, column 4).
27. Clump analysis (Region 2): candidate clumps can only just supply the remaining stars (row 7, column 1).
28. Row completion: 1 star needed, 1 candidate (row 7, column 7).
29. Mark 1 cell adjacent to stars as X (row 6, column 6).
30. Three candidates in a column: Middle cell can't hold a star (row 3, column 6).
31. Column completion: 2 stars needed, 2 candidates (row 2, column 6).
32. Mark 2 cells adjacent to stars as X (row 1, column 5).
33. Column completion: 1 star needed, 1 candidate (row 4, column 6).
34. Mark 1 cell adjacent to stars as X (row 4, column 5).
35. 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).
36. 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).
37. Three candidates with two adjacent: Isolated candidate must hold a star (row 1, column 2).
38. Mark 3 cells adjacent to stars as X (row 1, column 1).
39. Clump analysis (Region 10): candidate clumps can only just supply the remaining stars (row 4, column 2).
40. Three candidates with two adjacent: Isolated candidate must hold a star (row 6, column 3).
41. Mark 2 cells adjacent to stars as X (row 6, column 2).
42. Region completion: 1 star needed, 1 candidate (row 6, column 1).
43. Row 6 complete: Mark 1 remaining cell as X (row 6, column 5).
44. Three candidates in a column: Middle cell can't hold a star (row 9, column 5).
45. Region completion: 1 star needed, 1 candidate (row 10, column 5).
46. Column completion: 1 star needed, 1 candidate (row 8, column 5).
47. Mark 1 cell adjacent to stars as X (row 8, column 4).
48. Region complete: Mark 2 remaining cells as X (row 9, column 3).
49. Three candidates in a column: Middle cell can't hold a star (row 2, column 4).
50. Region completion: 1 star needed, 1 candidate (row 1, column 4).
51. Row 1 complete: Mark 2 remaining cells as X (row 1, column 9).
52. Row completion: 1 star needed, 1 candidate (row 2, column 10).
53. Mark 1 cell adjacent to stars as X (row 3, column 10).
54. Column completion: 1 star needed, 1 candidate (row 3, column 4).
55. Mark 2 cells adjacent to stars as X (row 3, column 3).
56. Row 3 complete: Mark 2 remaining cells as X (row 3, column 1).
57. Region completion: 1 star needed, 1 candidate (row 4, column 1).
58. Column 1 complete: Mark 3 remaining cells as X (row 8, column 1).
59. Column completion: 1 star needed, 1 candidate (row 8, column 3).
60. Mark 1 cell adjacent to stars as X (row 8, column 2).
61. Region completion: 1 star needed, 1 candidate (row 10, column 2).
62. Row 10 complete: Mark 2 remaining cells as X (row 10, column 9).
63. Column completion: 1 star needed, 1 candidate (row 9, column 9).
64. Mark 1 cell adjacent to stars as X (row 9, column 10).
65. Solved! Every row, column, and region has its two stars, none touching.