Star Battle

How to play Star Battle

Star Battle is a placement logic puzzle played on a square grid that is carved into a set of bold-bordered, irregularly-shaped regions — one region for every row (and column) of the grid. Your job is to place stars so that every row, every column and every region ends up holding exactly the right number of stars, while no two stars ever touch each other, not even at a single shared corner. It looks deceptively simple once you see a finished grid, but working out where the stars must go is a satisfying chain of pure deduction: every clue you need is already on the board in the shape of the regions themselves. This version ships three sizes — a friendly 6×6 with one star per line, a tougher 8×8 also at one star per line, and a full 10×10 challenge that raises the requirement to two stars per row, column and region. Every puzzle is generated fresh and machine-checked to have exactly one solution before it ever reaches you, so if you ever get stuck, the answer can always be found by logic alone.

The goal

Place stars on the grid so that three conditions hold everywhere at once: every row contains exactly the target number of stars, every column contains exactly the target number of stars, and every one of the bold-bordered regions contains exactly the target number of stars too. On Easy and Medium that target is one star per row, column and region; on Hard it rises to two. On top of the counting rules, no two stars may ever be placed in cells that touch — including cells that only share a corner. When every row, column and region holds its exact quota and no stars are touching, the puzzle is solved.

The rules

• One star count for the whole grid. Depending on difficulty, every row must contain exactly one star (Easy, Medium) or exactly two stars (Hard) — never more, never fewer once the grid is complete.
• Same count for every column. Exactly the same number of stars — one on Easy/Medium, two on Hard — must appear in every column as well, no matter how the rows are filled.
• Same count for every region. Each bold-bordered region must also contain exactly that many stars. Regions are irregular shapes, not simple rows or blocks, so a region can wind across several rows and columns — but wherever its cells lie, its star count must match the target exactly.
• No touching, not even diagonally. Two stars can never sit in adjacent cells — horizontally, vertically, or diagonally. A star at (row 3, column 4) forbids stars at all eight neighbouring cells, including the diagonal ones at (row 2, column 3) and (row 4, column 5). This single rule does more than anything else to narrow down where stars can go.

Making moves

Tap any cell to cycle it through three states: empty becomes a star, a star becomes a small dot mark, and a dot mark clears back to empty. The dot mark is purely a memory aid — mark a cell with a dot to remind yourself 'no star can go here' without it counting as a mistake or affecting whether you have won; only stars matter for winning. The board is divided into bold-bordered regions so you can see at a glance where each region begins and ends, with thin lines separating cells that share the same region and thick, bright lines marking every region boundary. As you place stars, any cell that currently breaks a rule — two stars touching, or a row, column or region that already has too many stars — is ringed in red so you can catch and undo mistakes quickly. A running timer and mistake counter sit above the board, and you can start a fresh puzzle, switch size, or jump to today's shared Daily Puzzle at any time.

Solving techniques

• Use the no-touch rule around every star you place. The instant you're confident about a star, immediately dot-mark all eight surrounding cells — they can never hold a star, so crossing them off shrinks the puzzle right away and often forces the next star's position in a neighbouring row or region.
• Hunt for regions with few open cells. A tiny or narrow region that must contain a star (or two, on Hard) but only has a couple of legal cells left is usually the fastest place to make a certain move. Scan for the smallest regions first.
• Watch rows and columns that are almost full. Once a row or column already holds its full quota of stars, every other empty cell in that line can be dot-marked immediately — it can never take another star, whatever region it belongs to.
• Look for forced lines inside a region. If a region's cells all lie within one or two rows or columns, then those rows/columns must supply that region's stars — which often means other regions cannot also place a star in the same row or column, narrowing their options too.

Winning and scoring

You win the instant every row, column and region holds exactly its target star count with no stars touching — the app checks continuously and shows a win banner the moment your last correct star lands. Your score rewards speed and accuracy: it starts at a base of 10000 and subtracts 5 points for every second on the clock plus 200 points for every mistake, never dropping below 1. In formula terms, score = max(1, min(99999, 10000 − seconds × 5 − mistakes × 200)). A mistake is counted only when you place a star on a cell where the puzzle's unique solution has no star — dot-marks and clearing a cell are never mistakes, so feel free to mark freely as you reason. Sign in to save your best score per size to the online leaderboard; otherwise your best result stays on this device.

Strategy tips

• Start with the smallest or oddest-shaped regions — a region squeezed into a corner or a single narrow strip usually has very few legal cells for its star, giving you an easy, certain first move.
• Chain your dot-marks. Every star you confirm should immediately dot-mark its eight neighbours and, once a row/column/region hits its quota, every other cell in that line or region too. This habit turns one confident star into several free deductions.
• Save uncertain corners for last. When two or three cells all look equally plausible for a region's star, leave that region alone and solve the rest of the board first — the extra constraints from surrounding rows and columns usually eliminate all but one candidate by the time you come back to it.

Frequently asked questions