How to play
Star Battle
Make space
for every star.
One star in every row, column and region. None touching, even at corners. Let’s find them without guessing.
Its shadow shows where another star cannot go.
One star. A little space.
Every row, column and thickly outlined region needs exactly one star. The small numbers name regions; they are not star counts.
Suppose a star went at r5c5. Its row, column and region could hold no others. Neither could any touching square — even across a border, even at a corner.
Could another star go at r4c4 beside this example?
Choose an answer to check your reasoning.
Read the answer
Right. r4c4 shares a corner with the example at r5c5. A region border never cancels the no-touching rule.
Hollow star + amber shade = an example only. No star has been proved.
Two places. One shared certainty.
Region 5 has two squares: r5c5 and r5c6. We do not know which holds its star.
Compare their shadows. Either position rules out the rest of row 5, plus r4c5, r4c6, r6c5 and r6c6. Those shared squares can be crossed now.
Can we place the star in the two-cell region yet?
Choose an answer to check your reasoning.
Read the answer
Exactly. The shared crosses are certain; the star is not. r5c5 and r5c6 both remain candidates until another fact separates them.
Keep both possibilities. Only their shared exclusions become facts.
Look where those crosses land.
Follow the same two crosses into region 6. This region has three squares: r6c5, r6c6 and r7c6.
The first two are now empty. Which square can still hold the one star region 6 needs?
Where must region 6 put its star?
Choose an answer to check your reasoning.
Read the answer
Yes. r6c5 and r6c6 are both crossed by the shared exclusion. Only r7c6 remains in region 6. We can place that star next.
Nothing new placed yet. Use the crosses we have already proved.
Now the first star is certain.
Region 6 needs one star. r6c5 and r6c6 are crossed, so r7c6 is its only place.
Place it, then follow the exclusions spreading from it. Its whole row, column and region are full; its touching neighbours must stay empty.
Why every other square in region 6 is empty
- r6c5: ruled out by every earlier possibility.
- r6c6: ruled out by every earlier possibility.
Solid star = proved. Green × = proved empty. A blank is still undecided.
One star helps its neighbour.
Region 3 has four squares. r7c4 and r7c5 share the first star’s row. r8c5 touches that star at a corner. All three are out.
Only r8c4 remains. That is where region 3 must put its star.
Why every other square in region 3 is empty
- r7c4: same row as r7c6.
- r7c5: same row as r7c6.
- r8c5: touches r7c6, even at a corner.
A neighbouring region gets its own star, with space between them.
The small region can answer now.
Return to region 5, our original two-square choice. r5c6 lies in column 6, which already has the star at r7c6.
That rules out r5c6. Now — and only now — r5c5 is forced.
Why every other square in region 5 is empty
- r5c6: same column as r7c6.
The region did not change. New information resolved its uncertainty.
Read the spaces that remain.
Move up to region 2. The star at r5c5 excludes its column-5 squares. The star at r7c6 excludes its column-6 square.
r2c4 shares column 4 with r8c4. Only r2c3 remains uncrossed in region 2. Place its star.
Why every other square in region 2 is empty
- r1c5: same column as r5c5.
- r2c4: same column as r8c4.
- r2c5: same column as r5c5.
- r2c6: same column as r7c6.
The proof ledger below accounts for every crossed alternative.
Wherever it goes, this is empty.
Region 4 still has three possibilities: r4c1, r4c2 and r6c1. Do not choose one yet.
A star in either column-1 position forbids r3c1 by column. A star at r4c2 forbids r3c1 by corner contact. So all three agree: r3c1 is empty.
A shared exclusion can combine different reasons. It needs every alternative.
That one cross unlocks the corner.
Region 8 had just r1c1 and r3c1 left. The other squares were excluded by our known stars.
The new cross removes r3c1. Only r1c1 remains, so the corner gets a star.
Why every other square in region 8 is empty
- r1c2: touches r2c3, even at a corner.
- r1c3: same column as r2c3.
- r1c4: touches r2c3, even at a corner.
- r2c1: same row as r2c3.
- r2c2: same row as r2c3.
- r3c1: ruled out by every earlier possibility.
One carefully proved empty square can be as useful as a star.
Carry the column through.
The new star fills column 1. Cross out r4c1 and r6c1 in region 4.
Of its three earlier possibilities, only r4c2 remains. Place its star and let the next exclusions spread.
Why every other square in region 4 is empty
- r3c2: touches r2c3, even at a corner.
- r3c3: same column as r2c3.
- r3c4: touches r2c3, even at a corner.
- r4c1: same column as r1c1.
- r5c1: same column as r1c1.
- r6c1: same column as r1c1.
- r6c3: same column as r2c3.
- r7c1: same column as r1c1.
- r7c2: same row as r7c6.
- r7c3: same column as r2c3.
- r8c1: same column as r1c1.
- r8c2: same row as r8c4.
- r8c3: same column as r2c3.
Borders separate region quotas, not the row and column rules.
Many crosses. One clear opening.
The large region 1 winds through the centre. Its thick border has stayed exactly the same.
Earlier stars have excluded every square in it except r3c7. The highlighted opening is its only remaining place for a star.
Why every other square in region 1 is empty
- r1c6: same row as r1c1.
- r1c7: same row as r1c1.
- r1c8: same row as r1c1.
- r2c7: same row as r2c3.
- r2c8: same row as r2c3.
- r3c5: same column as r5c5.
- r3c6: same column as r7c6.
- r4c3: same column as r2c3.
- r4c4: same row as r4c2.
- r4c5: same row as r4c2.
- r4c6: same row as r4c2.
- r5c2: same column as r4c2.
- r5c3: same column as r2c3.
- r5c4: same row as r5c5.
- r6c2: same column as r4c2.
- r6c4: touches r5c5, even at a corner.
Inspect the ledger if you want to trace each alternative back to its reason.
The last star still needs a reason.
Region 7 runs down the right edge. Its other squares are crossed by the seven stars already placed.
Only r6c8 remains. Its star finishes every quota without touching another star. Every star has followed a reason.
Why every other square in region 7 is empty
- r3c8: same row as r3c7.
- r4c7: same column as r3c7.
- r4c8: touches r3c7, even at a corner.
- r5c7: same column as r3c7.
- r5c8: same row as r5c5.
- r6c7: same column as r3c7.
- r7c7: same column as r3c7.
- r7c8: same row as r7c6.
- r8c6: same column as r7c6.
- r8c7: same column as r3c7.
- r8c8: same row as r8c4.
The final star follows the same one-place-left rule as the first.
Eight stars. Every promise kept.
Count one in each row, one in each column and one in each outlined region. Check the space around every star.
You have followed the whole puzzle from two uncertain positions to eight certain stars. Now try a different board with a two-cell region of its own.
Crosses are useful notes. Our game accepts a correct board without every empty square marked.
Find your own eightA new sheet.
Your eight stars.
A different 8 × 8, with no stars filled in. Start by comparing the two squares of region 1. What do their possible stars both rule out?
Practice stays in this page’s memory. Reloading starts fresh. Your regular game and saved progress are separate.
0 stars placedUnassisted attempt
Tap a square to use the selected tool. A blank is undecided.
Clear this practice board and start a new attempt? You can undo the reset.
How to place and mark
Choose Star, Mark × or Erase, then tap a square. Tap again to remove that choice. Crosses are your notes; they are optional for completion. Mistakes stay editable.
Keyboard: Tab into the board, arrows to move, Enter or Space to use your tool. S places a star; X marks empty; Delete or Backspace erases. Tab leaves the board.
Explain a move checks the current stars and crosses. It marks an attempt assisted when it proves a move, even before you Apply. A contradiction asks you to revise your choices; it does not replace them.
Let the next star
have a reason.
Keep the possibilities open. Cross only what every case forbids. Then look for the one place left.
Play Star Battle Return to your practiceFree to play. No account needed.
The quick rules.
- One star in every row. Exactly one, not just at most one.
- One star in every column. Distance does not allow a second star.
- One star in every outlined region. Thick borders define regions. Their small numbers are names, not clues asking for that many stars.
- No stars touching. They cannot share a side or corner, even in different regions. Farther-apart stars on the same diagonal are allowed.
This site uses the one-star 8 × 8 variant. Eight rows means eight stars in total. Crosses are optional solving notes.
Back to the guided lessonA little more clarity.
Does a small region give me a star immediately?
Only if exactly one square remains possible. A two-cell region can still have two alternatives. Compare what both forbid before choosing either one.
Do region borders block the spacing rule?
No. A star excludes all eight touching squares regardless of their regions. A border changes region membership, not adjacency.
Are blank squares and crosses the same?
No. Blank means undecided; a cross records that you believe the square is empty. You can finish with blank unused squares. A mistaken cross can block a correct star; erase or undo it.
How do I recover from a mistake?
Undo a recent move, or use Erase. Explain a move checks your current attempt and reports a contradiction when no completion remains. It will not silently correct your marks.