Star Battle

Place stars so that every row, every column and every region holds the same number of them, and no two stars touch, not even at a corner. Heavy lines divide the regions; their tints only tell neighbors apart. How many stars is the game mode:

• One star: One in each, the puzzle also known as Queens.
• Two stars: Two in each, the puzzle also known as Two Not Touch.
• Three stars: Three in each.

Controls

On a touch screen, a tap does what a click does, and a long press what a right-click does (more ways to right-click).

Click a square to put a star there (click again to cross it out, and again to clear it). Right-click it to cross it out (click again to put a star there, and again to clear it). Keep the button down and drag to do the same to every square you pass over that looked the same as the first.

With the keyboard, the arrow keys move a cursor around the board. Enter does what a click does to the square under it, and Space what a right-click does. Press Backspace or Delete to clear it; clicking it round gets there too.

A cross is your own note that a square holds no star. You need not cross anything out to finish: the puzzle is solved as soon as the stars are all in place. A star turns red when it touches another, or when its row, column or region holds too many.

A star rules out the blank squares touching it, and the rest of its row, column or region when the star is the last one that holds. With Cross out the squares a star rules out turned on in the preferences, those marks are made for you as you place: one Undo takes back the placement and the marks together, and taking the placement away later leaves the marks for you to clear.

Where the puzzles come from

Star Battle was invented by Hans Eendebak for the 2003 World Puzzle Championship.

Hints

Hint explains the next step rather than simply making it. Each step decides one or more squares from the regions and from the stars and crosses you have already placed, so it carries on from wherever you are.

• A ring marks the squares the step decides. The sentence says what they must be.
• An outline marks what else it reasons from: a star, a region, or the squares a star would rule out.
• Stripes mark the row, column or region the step is about, or several rows or columns counted together.

A hint calls a square open while it holds neither a star nor a cross, so its first steps are often the crosses a star you placed gives: the squares touching it, and the rest of a row, column or region that has all its stars.

The steps after those, easiest first:

• A row, column or region with exactly as many open squares as it still needs stars has a star in each. One that would not have room for its stars without a certain square has a star there. Stars cannot touch, so two open squares that touch, even at a corner, have room for only one.
• A region whose open squares all lie in one row or column must put its stars there, so when that row or column needs no more than those, its other squares are empty. The same holds the other way round, for a row or column whose open squares all lie in one region.
• A star that would touch so many open squares of a row, column or region that too few are left for the stars it needs cannot be there.
• On Normal boards, several rows or columns side by side are counted together: when the regions lying wholly inside them need as many stars as those rows do, the rows’ other squares are empty, and when the regions reaching into them need no more than the rows do, those regions’ squares outside the rows are empty.
• On Tricky boards, a star is tried in a square where it would complete its own row, column or region. If the squares that rules out leave another row, column or region without room for its stars, the square is empty.

If a square you marked is wrong, the hint asks you to fix the highlighted mistakes first.

Not in this game

• Turning the board to fit the screen. The grid is square, so it is the same shape either way round.

Star Battle parameters

These parameters are available from the ‘Custom type…’ option on the ‘Type’ menu.

Grid size

Width and height of the grid, which is also how many regions it is divided into. It must be at least 4 with one star, 8 with two and 12 with three, and at most 26. A grid wider than 10 can take several seconds to appear, a much larger one minutes, and the harder puzzles longer. It must be between 4 and 26.

Game mode

Which puzzle to play: One star, Two stars or Three stars. The rules of each are at the top of this page.

Difficulty

Determine the difficulty of the generated puzzle; see what the names mean.

Easy puzzles can be finished by looking at one row, column or region at a time, or at one row or column and the regions in it.

Normal puzzles need several rows or columns side by side counted against the regions in them.

Tricky puzzles need a star tried in a square: it would complete its own row, column or region and leave another without room.

More help

• Features every puzzle shares: hints, checking your work, checkpoints, playing by touch
• Help home