Star neighbors, Finished and Last squares
Page 1 of How to Solve Star Battle Puzzles.
Three moves do most of the work in every Star Battle puzzle: Star neighbors, Finished and Last squares. They need no counting beyond "how many stars does this still need?" The first page of the guide showed each one once. This page shows them on rows, columns and regions, and gives you a routine for finding them fast.
You'll use all three in every puzzle. In the app, every one of the 22,058 puzzles uses each of them, at every size.
The examples are a 10×10 one-star puzzle from the app. Rows and columns are numbered from 1 at the top left.
Star neighbors
Stars cannot touch, not even at a corner. So a new star rules out the squares around it. Put a dot on each of them. A star in the middle of the board has eight neighbors. A star on an edge has five, and a star in a corner has three.
Star neighbors: Rule out the squares around this star.
Do this at once, every time you place a star. The dots are what make the next two moves work.
Finished
A row, a column or a region is finished when it holds all its stars. In a one-star puzzle, that means one star. Rule out every open square that is left in it. An open square is a square with no mark yet.
A new star finishes three things at once: its row, its column and its region. Check all three.
Finished: This row has all its stars. Rule out its open squares.
Finished: This column has all its stars. Rule out its open squares.
A region works the same way. This star is in a different part of the board.
Finished: This region has all its stars. Rule out its open squares.
Last squares
Count the open squares in a row, column or region. If it has as many open squares as it has stars left, each of them must be a star. In a one-star puzzle, that is a single open square with one star left.
Ruling out squares is what makes this work. Each dot takes one square away from the count.
Last squares: This region has one open square and one star left. That square must be a star.
Last squares: This row has one open square and one star left. That square must be a star.
Last squares: This column has one open square and one star left. That square must be a star.
A routine for finding them
Go through these steps after every star:
- Dot the neighbors. Put a dot on each square around the new star. The app does this for you.
- Check its row, column and region. Each one is now Finished. Dot the open squares that are left.
- Look at everything that just lost a square. Each new dot is in a row, a column and a region. Count the open squares in those three. If one has a single open square left, it is a Last square.
- Place that star and begin again at step 1.
Look only at the rows, columns and regions that changed. They are the only ones that can have a new Last square.
The same routine on an 8×8 puzzle
Here is the routine on a smaller board.
Row 2 has a single open square. That is a Last square.
Last squares: This row has one open square and one star left. That square must be a star.
Next, dot the neighbors of the new star.
Star neighbors: Rule out the squares around this star.
Then check its region.
Finished: This region has all its stars. Rule out its open squares.
Then its column.
Finished: This column has all its stars. Rule out its open squares.
These moves are not all that a puzzle needs. When none of them applies, the next page shows two more: Region inside a line and Line inside a region.
Practice on puzzles like these in our Star Battle Puzzles app, for iPhone, iPad, Mac and Android.
