STAR BATTLE · TWO NOT TOUCH · VERIFIED UNIQUE SOLUTIONStar Battle puzzle online
Place one star in every row, one in every column, and one in every outlined region. The final restriction is the one that makes the board snap into focus: stars may not touch at an edge or a corner. This browser version uses independently verified source boards, deterministic Practice URLs, explicit Star and X tools, autosave, Hint, Check, Undo and Redo.
What Star Battle asks you to track
Star Battle, sometimes called Two Not Touch, is a region-and-spacing logic puzzle. Every row has exactly one star. Every column has exactly one star. Every bold outlined region has exactly one star. Two stars can never share an edge or corner. Those four constraints overlap constantly, so the puzzle is less about guessing a location and more about proving where a star cannot go.
The X tool is therefore as important as the Star tool. Crossing out impossible cells exposes the remaining capacity of a row, column or region. When a line or region has only one candidate left, its star becomes forced and the no-touch rule immediately removes up to eight neighboring cells.
Verified instead of assumed
V0.103 freezes 45 source puzzles across 6×6, 7×7 and 8×8 boards. Every source is counted by an exact solver that simultaneously enforces row quota, column quota, region quota and the eight-neighbor no-touch rule. A source enters the frozen bank only when that solver finds exactly one complete placement.
The independent verifier then transforms every source through all eight square symmetries and recounts the result, producing 360 verified playable variants. Practice selection is deterministic once the URL seed is fixed, so the same URL recreates the same source and symmetry for replay, sharing and QA.
How to solve a Star Battle board
Begin with the smallest or most constrained regions. A narrow region squeezed across only a few rows or columns can restrict multiple lines at once. If all cells of a region lie inside two rows, that region’s one star must occupy one of those rows; this can combine with other regions to reserve or eliminate row capacity even before you know the exact star cell.
Next use the no-touch rule aggressively. A confirmed star eliminates every orthogonal and diagonal neighbor. On compact boards this often cuts a region in half or leaves a row with one legal candidate. When a row already contains its star, mark every other cell in that row X. Do the same for columns and regions. These simple completion rules are the foundation for longer deductions.
A strong habit is to reason with groups rather than individual cells. If two adjacent candidate cells in a region occupy the same two columns, that region’s star claims one of those columns even before you know which cell. Similar row-region and column-region interactions are what separate harder boards from simple scanning.
Easy, Medium and Hard are measured
The generator does not assign difficulty only from board size. For each size it builds many exact-unique connected-region partitions and records the independent solver’s search effort. The lowest-effort verified candidates form the Easy pool, candidates near the center form Medium, and the highest-effort verified candidates form Hard.
That does not pretend to measure every human solving technique, but it gives the labels a reproducible basis. A 6×6 Hard board can demand more branching interaction than a simple 7×7 Easy board, while still using the same transparent rules.
Connected regions matter
Every outlined region is generated as a connected group of cells. The generator starts from the known solution stars and grows each region outward while repeatedly checking that the puzzle still has exactly one solution. Adding a cell to a region can create a new alternative star placement, so the generator rejects any growth step that breaks uniqueness.
This incremental method means the final irregular shapes are not decorative. Their boundaries carry the exact information that distinguishes the one valid star placement from every alternative.
Practice workflow
Choose 6×6 for a compact warm-up, 7×7 for the default balance, or 8×8 for a roomier deduction chain. Pick Easy, Medium or Hard, then use Fresh Practice whenever you want a new deterministic seed. The URL records size, difficulty and seed, so reopening it rebuilds the same puzzle rather than silently swapping the board.
Use Star to place a confirmed star, X to mark an eliminated cell, or Clear to remove a mark. Right-clicking a cell jumps directly to X on desktop. Keyboard users can focus a cell and press S or Space for a star, X for an exclusion, and E/Delete/Backspace to clear. The board uses thick borders where region membership changes, so region shapes remain readable on touch screens.
Hint fills the next incorrect or missing state from the verified solution. Check reports current conflicts or remaining star count. Undo, Redo and Restart are available for learning, but these assistance tools mark the run Assisted so Clean local records remain separate.
Autosave and local records
Each exact Practice seed has its own browser-local autosave. State, move count, assistance status, source and symmetry are restored only when they match the current puzzle contract. The specialist tracks solved boards, Clean solves, a local best for each size-and-difficulty setup, and a separate Daily streak.
These are personal browser-local records, not a fabricated global rank, percentile or public leaderboard.
Why X marks are useful
Star Battle is often solved through elimination long before the final stars appear. An X records a proof: this cell is impossible because the row is complete, the column is complete, the region is complete, or it touches a confirmed star. Keeping those exclusions visible makes group deductions easier and reduces repeated mental work.
The app never requires every non-star cell to be marked X before completion. The solved condition is based on the star constraints themselves.
Common mistakes to avoid
Do not stop after satisfying rows and columns. A permutation with one star per row and column can still violate a region quota or place two stars diagonally adjacent. Do not treat region borders as decoration, and do not forget that corner-touching stars are forbidden. Also avoid filling a tempting cell just because it fits locally; check what it does to the row, column, region and neighboring candidates together.
When stuck, scan completed units first, then small regions, then pairs of rows or columns whose remaining candidates overlap a small set of regions. Star Battle rewards systematic elimination more than speculative moves.