Galaxies
Divide the grid into symmetric regions
Galaxies (also known as Tentai Show) is a beautiful region-division puzzle where you partition a grid into "galaxies" — regions that have perfect 180-degree rotational symmetry around their center dot. Each dot on the grid marks the center of a galaxy, and you must draw borders so that every cell belongs to exactly one galaxy with the correct symmetry. The visual nature of this puzzle makes it uniquely appealing: you can often "see" the symmetry before you prove it logically.
How to Play Galaxies
Center Dots
Each dot on the grid marks the rotational center of a galaxy. Dots can be in cells, on edges, or at cell corners.
Rotational Symmetry
Each galaxy must have perfect 180-degree rotational symmetry around its center dot. If cell A is in a galaxy, its mirror through the center must also be.
Complete Coverage
Every cell in the grid must belong to exactly one galaxy. No cell is left unassigned.
Connected Regions
Each galaxy must be a connected region — you can reach any cell from any other by moving through adjacent cells in the same galaxy.
Draw Borders
Draw borders between cells to separate galaxies. Borders run along cell edges.
Use Symmetry
Once you assign a cell to a galaxy, its symmetric partner through the center dot is also assigned. This is the key deduction mechanism.
Strategy & Solving Tips
Solving Galaxies is fundamentally about understanding how rotational symmetry constrains cell assignment. These techniques help you partition the grid efficiently.
- Dots on cell edges or corners create galaxies with specific shapes — a corner dot creates a 4-cell galaxy, an edge dot creates a 2-cell galaxy
- Start with dots near the grid border: their galaxies can only expand inward, limiting possibilities
- If a cell can only belong to one galaxy (all other dots are too far or would break symmetry), assign it immediately
- Large galaxies propagate quickly: adding one cell forces its symmetric partner, which may force more cells
- Look for conflicts: if two galaxies would overlap when expanded symmetrically, at least one must be smaller
- Work from constrained areas (corners, edges) toward the center where more options exist
Galaxies FAQ
What is 180-degree rotational symmetry?
If you rotate the galaxy shape 180 degrees around its center dot, it looks identical. Think of it like spinning the shape halfway around — it must map perfectly onto itself.
Can a galaxy be just one cell?
Yes, if a dot is in the center of a cell, that single cell is a valid galaxy. It's trivially symmetric.
What if a dot is on a cell edge?
A dot on an edge between two cells means the galaxy must include both cells (and their symmetric partners). Edge dots create galaxies with an even number of cells.
How do I know if my partition is wrong?
Check each galaxy for rotational symmetry and connectivity. If any galaxy fails either test, something is wrong. Also ensure no cells are unassigned or double-assigned.
Similar Puzzles You Might Enjoy
NoriNori
Another region-based puzzle where you shade cells within regions following strict placement rules.
LITS
Place shapes in regions with connectivity and adjacency constraints — similar region-division thinking.
Yin-Yang
A two-color puzzle with connectivity constraints that also rewards visual-spatial reasoning.
Ready to Play Galaxies?
Discover the visual beauty of Galaxies — where rotational symmetry guides you to the one correct partition. A puzzle you can feel as much as solve.