Galaxies Solver

Galaxies Solver — Step by Step

Click to place each dot — in the middle of a square, on a side, or on a corner. Then press Solve. Or play a generated puzzle and send it here with one click.

Galaxies Solver: rules, how to use it, tips

Split the grid into galaxies, each holding one dot and looking the same after a half turn around it.

The rules

Every square must belong to exactly one galaxy.
Each galaxy contains exactly one dot.
Each galaxy has rotational symmetry around its dot: turn it 180° around the dot and it lands exactly on itself.
Galaxies are joined pieces — no galaxy is split in two.

Using the solver

Choose the size and click where each dot is (or press Sample). Click a dot again to remove it.
Press Solve and step through: the squares each dot touches, mirror images, squares only one dot can reach, and what-ifs.

Tips

Start at the dots. A dot in a square owns that square. A dot on a line owns both squares beside it. A dot on a corner owns all four squares around it.
Mirror everything. Whenever a square joins a galaxy, its partner — the square the same distance from the dot on the opposite side — joins too.
Off the edge. A square can't join a dot if its mirror image would land outside the grid or on a square already taken.
Who can reach it?. If only one dot can claim a square, that square is theirs.

The full guide, with a worked example and common mistakes: How to play Galaxies.

Questions

Do galaxies have to look like spirals?

No — any shape works as long as it looks the same after a half turn around its dot. Many are rectangles, crosses or zig-zags.

What does auto-mirror do?

When you paint a square, the matching square on the opposite side of the dot is painted too.

Is there always one answer?

Yes — every puzzle here is checked to have exactly one way to split the grid.

How do I solve one from a book?

Open the Galaxies Solver, click where the dots are and press Solve.