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Star Battle Online
Also known as Two Not Touch
Daily Logic Challenge • 2026-09-09

Star Battle Online

Place stars so every row, column, and outlined region has the required count. No two stars may touch, not even diagonally!

🔥0-Day StreakOctober: 0/31
2★ per Row/Col/Region
⏱️00:00
Stars:0 / 20
20 remaining
💡 Swipe across cells in Cross mode to multi-fill
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Daily Archive
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Interactive Solver
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Rules & Strategies
Master 2-star logic tricks, traps, and deductions

What is Star Battle (Two Not Touch)?

Star Battle—widely recognized across the United States as Two Not Touch—is an internationally acclaimed pencil-and-paper logic puzzle celebrated for its elegant simplicity and profound mathematical depth. Unlike number-placement puzzles such as Sudoku or Kakuro, Star Battle is a purely spatial, binary constraint-satisfaction challenge. There are no arithmetic calculations, no numerical sequences, and no arbitrary guesswork. Every deduction is rooted in geometry, counting parity, and non-touching spatial exclusions.

The puzzle was originally conceived in 2003 by the legendary Dutch puzzle architect Hans Eendebak for the 12th World Puzzle Championship (WPC) held in Arnhem, Netherlands. Since its international tournament debut, Star Battle has grown into one of the core competitive events administered by the World Puzzle Federation (WPF). Over the past two decades, its popularity has exploded worldwide, inspiring newspaper puzzle columns, educational math competitions, and digital adaptations like LinkedIn Queens and mobile variants.

A standard Star Battle grid consists of an N × N square matrix partitioned into exactly N distinct, contiguous geometric shapes termed “regions” or “rooms”. Your objective is deceptively straightforward: strategically place a designated number of stars (K stars per unit, where typically K = 1 for beginner 8 × 8 boards and K = 2 for classic 10 × 10 tournament boards) such that every row, every column, and every bordered region contains the exact required star quota.

The Fundamental Rules of Star Battle

To solve any Star Battle puzzle successfully, you only need to master three interrelated, immutable constraints:

1. Row Quota

Every horizontal row must contain exactly K stars (e.g., exactly 2 stars in classic 10x10). No row may have fewer or more stars.

2. Column Quota

Every vertical column must contain exactly K stars. Star distribution is balanced across the entire width of the grid.

3. Region Quota

Each boldly outlined polyomino region must contain exactly K stars, regardless of its shape, size, or orientation.

The Core Adjacency Rule: No Two Stars May Touch

This is the defining rule that gives the puzzle its name, Two Not Touch. Stars cannot be placed in adjacent cells in any direction: horizontally, vertically, or diagonally. When you confirm a star in a cell at coordinate $(r, c)$, all eight surrounding cells $(r \pm 1, c \pm 1)$ are instantly invalidated and must be marked with a cross (✕). This diagonal restriction is crucial—it turns simple line packing into an intricate web of geometric blockades.

Master Solving Strategies & Deductive Techniques

Novice players often struggle because they attempt to randomly guess placements. Experienced tournament solvers never guess. They use rigorous constraint propagation techniques to eliminate impossible cells. Here are the four master techniques used by champion solvers:

Technique 1The Pigeonhole Overlap Deduction (Line-Region Reduction)

Consider a 2-star puzzle on a 10 × 10 board. Because stars cannot touch, any region confined within two adjacent rows (for example, rows 1 and 2) can hold at most 2 stars. If you identify two distinct regions that are both completely contained within rows 1 and 2, those two regions together require 2 + 2 = 4 stars. Since rows 1 and 2 collectively require exactly 4 stars (2 stars/row × 2 rows = 4 stars total), all 4 stars for those two rows must reside inside those two regions! Consequently, every other cell in rows 1 and 2 outside those two regions can be immediately eliminated with a cross (✕).

Technique 2The 1-Cell Thickness Barrier & Squeeze Logic

If a region or a subset of a region forms a straight corridor of 3 cells (for example cells at col 1, col 2, col 3 on row r), notice what happens if you place a star in the middle cell (r, 2). The middle star eliminates both adjacent neighbors (r, 1) and (r, 3). Thus, a 3-cell linear strip can contain at most one star. More generally, a linear strip of length L can contain at most ⌈L / 2⌉ stars. If a 2-star region has only 4 available cells in a line, you know the stars must occupy alternating positions.

Technique 3Corner Traps & Diagonal Star Formations

In a 2 × 2 square block of four cells, you can place at most one star. If you placed two stars in a 2 × 2 block, they would either be in the same row, the same column, or touch diagonally—all of which are illegal. If a region has a 2 × 2 block that must contain a star, any cell outside that block that touches all four cells diagonally or orthogonally cannot contain a star.

Technique 4Global Parity Counting (Row-Column Alignment)

When isolated deductions stall, step back and examine the top 3 rows or the leftmost 3 columns. The top 3 rows of a 10 × 10 board require exactly 3 × 2 = 6 stars. Count how many regions intersect those 3 rows. If 3 regions are fully enclosed within those rows, and a 4th region has only 2 cells peeking into row 4, counting the total star capacity immediately tells you whether stars must be inside or outside the overflow cells.

How Star Battle Compares to Sudoku and Queens

Many puzzle enthusiasts discover Star Battle after seeking alternatives to classical number games. While both share grid-based constraints, their cognitive demands differ significantly:

Puzzle TypeCore ElementsPrimary ConstraintThinking Style
Star Battle (Two Not Touch)Stars & Eliminations (Binary)Quota per line/room + No diagonal contactPure spatial deduction & region overlap counting
Classic SudokuDigits 1 through 9No duplicate numbers in row, column, or 3 × 3 boxSet elimination & numerical candidate tracking
LinkedIn QueensCrowns/Queens (1 per unit)1 Queen per row, col, color + no diagonal touchSimplified 1-star variation with colored shapes
Nonograms / PicrossFilled Blocks vs CrossesRun-length clues on row and column headersLine-by-line overlap shading and pixel art reveal

Because Star Battle requires zero numerical calculation, it is universally accessible across language barriers and age groups, making it a favorite tool among mathematics educators for cultivating deductive reasoning in students.

Play Online or Solve on Paper: Our Free Platform Features

Star Battle Online is engineered from the ground up for serious puzzle lovers who value speed, clean design, and complete freedom from intrusive advertisements:

⭐ Fresh Daily Challenges

A brand-new handcrafted 10x10 puzzle released every midnight with full streak tracking and historical archive access.

⚡ 15ms Interactive Solver

Input custom grid configurations into our online solver to inspect step-by-step logic proofs.

🎯 Multiple Size Formats

Progress smoothly from gentle 8x8 1-star grids to championship-grade 10x10 2-star puzzles.

🖨️ Clean Printable Worksheets

Export crisp, ad-free A4 PDF sheets via our printable generator for offline puzzle tournaments or classroom sessions.

Frequently Asked Questions

What is the difference between Star Battle and Two Not Touch?

Star Battle and Two Not Touch refer to the exact same logic puzzle. The name "Star Battle" was coined by Dutch puzzle designer Hans Eendebak when the puzzle debuted at the 2003 World Puzzle Championship. In North America and various puzzle publications, it is commonly titled "Two Not Touch" to emphasize the primary constraint: no two stars may touch horizontally, vertically, or diagonally.

Can stars touch diagonally in Star Battle?

No. The non-touching rule in Star Battle applies to all eight surrounding neighboring cells. Placing a star in any cell immediately eliminates the four orthogonally adjacent cells (top, bottom, left, right) and all four diagonally adjacent corner cells.

Does every daily puzzle have a unique verified solution?

Yes. Every puzzle featured on Star Battle Online is mathematically verified using constraint propagation and lookahead pruning to ensure exactly one unique solution exists. Guessing or trial-and-error is never required.

Is guessing ever required in Star Battle?

No. All properly constructed Star Battle puzzles can be solved entirely through deductive logic. If you find yourself guessing (bifurcating), you have likely overlooked a row-region counting deduction, a pigeonhole overlap, or an adjacent exclusion trap.

What is the best starting move in a 10x10 2-star puzzle?

The best opening strategy is to inspect narrow regions that span only one or two rows or columns. In a 2-star puzzle, any region constrained within two rows can absorb at most two stars. If two distinct regions both lie entirely inside the same two rows, all other cells in those two rows can be crossed out immediately.

How does Star Battle compare to Sudoku and Queens?

While Sudoku is based on placing numbers 1 through 9 into subgrids without duplicates, Star Battle is a purely spatial, binary deduction puzzle (each cell either contains a star or an elimination cross). LinkedIn Queens is a 1-star variation where each row, column, and colored region contains exactly one queen with no diagonal touching.

Where can I play Star Battle puzzles online for free?

Star Battle Online (starbattleonline.com) lets you solve Star Battle puzzles free in any browser, with no download or signup. It offers a new daily puzzle every day, an archive of 8x8 and 10x10 grids at two difficulty levels, a step-by-step solver, and free printable puzzle sheets with solutions.

What are the rules of Star Battle?

Place stars into a grid divided into outlined regions so that (1) every row, every column, and every region contains exactly the required number of stars (1 star on 8x8 grids, 2 stars on 10x10 grids), and (2) no two stars ever touch — not horizontally, not vertically, and not diagonally. Each puzzle has exactly one solution reachable by pure logic.

Is there a daily Star Battle puzzle like Wordle?

Yes. Star Battle Online publishes one handpicked daily puzzle every day at starbattleonline.com/daily, in the same once-a-day tradition as Wordle. Each daily puzzle is verified to have a unique solution, and the archive keeps growing so you always have another grid to solve.