Galaxies is a puzzle that combines logic and geometry.

Galaxies is a puzzle that combines logic and geometry.
The playing field, represented as a rectangular grid, symbolizes the universe filled with numerous scattered black holes.
Your task is to draw borders so that the entire grid is divided into symmetrical regions, each representing a galaxy.
As expected, there must be exactly one supermassive black hole located at the center of each galaxy.

If the term central symmetry is unclear, the image below shows examples of possible galaxy shapes in this puzzle:

How to solve

As with any logic puzzle, there is only one possible solution, and it can be reached purely through reasoning.

Let’s take this puzzle as an example:
https://en.grandgames.net/galaxies/id568408

First, you can remove the borders around black holes that lie directly on them rather than in the center of cells (right mouse button or the second button at the bottom).

The main solving process is best started from the corners and edges.
Since each black hole must be centered within its galaxy, the grid’s boundaries naturally restrict possible galaxy zones on one or two sides. Using symmetry, you can confidently draw the opposite boundary for some of them.
Also, remember that each galaxy must contain only one black hole, so there will always be a border between two adjacent holes—either vertically or horizontally.

Following this principle, the discovered galaxies provide hints for solving the neighboring cells.
It’s also important to note that there can’t be areas without a black hole — for example, cell (0,0) must belong to the hole located below it.

Focus on analyzing cells that are constrained on two sides.
Often, such cells can only belong to a single black hole, which helps determine the exact shape of that galaxy.
This way, you can identify the position of a few more regions:

Finally, by maintaining symmetry and considering the two-sided constraints of the black holes, you can find the remaining galaxies.

Try it yourself — it’s easy!
https://en.grandgames.net/galaxies/id568408