Rune Flow

The two rules that decide every board

Rune Flow belongs to a family of path puzzles often called number link or flow puzzles. There are only two rules: connect each pair of matching crystals with a continuous path, and cover every cell of the board. The second rule is the one new players forget, and it is also the one that makes the puzzle solvable by logic. Because every cell must be used exactly once, each board has a single intended layout rather than many loose ones.

Keeping the full-board rule in mind changes how you look at empty space. A small pocket of cells that no path can reach is not harmless; it means the current routes are wrong somewhere. Spotting those pockets early is the core skill.

Start where there is no choice

Look first at crystals in corners and along edges. A crystal in a corner has only two neighbouring cells, so its path has at most two ways to leave, and often only one of them makes sense. Crystals that are next to each other with no room around them can simply be joined directly. Every forced move you make removes options from the paths around it and creates more forced moves.

A useful rule of thumb is that paths hug walls and hug each other. Solutions rarely have gaps of a single cell between two parallel routes, because that cell would need its own path to fill it. When you see a route running along an edge, the neighbouring route usually runs right beside it.

When a long detour is right

Beginners connect pairs by the shortest route, and on small boards that often works. On larger layouts the shortest route usually leaves a strip of cells that nothing else can reach. In those cases one of the paths has to wind the long way round, filling the space as it goes. If you have joined every pair but a few cells are still empty, look for the path next to those cells and stretch it through them.

If two paths seem forced to cross, one of them is taking the wrong side of an obstacle. Back up to the point where that path had a choice and send it the other way. Crossings are impossible in a correct solution, so a forced crossing is a clear signal, not a dead end.

Playing the modes well

Levels and the Daily Challenge reward calm, careful reading. No Mistakes ends the run on one wrong move, so it is worth deciding each path fully before you draw it; think in whole routes rather than single cells. Speed Run rewards the opposite habit: draw the obvious corner and edge paths immediately, and let the leftover space tell you where the remaining routes must go. Star ratings reward efficiency, so drawing each path once, rather than redrawing it, matters as much as speed.

Why path puzzles are good for the brain

Flow puzzles train spatial planning and constraint reasoning: holding several partial routes in mind and checking them against each other. Because every board has one intended solution and no randomness, improvement is easy to feel. Levels that once took minutes start to fall in seconds, which is a large part of why the genre is so relaxing.

When can I play Rune Flow?

Rune Flow is out now on Google Play for Android, and it is free to download.

Is Rune Flow free?

Yes, it is free to play.

Do I have to fill the whole board?

Yes. A level is solved only when every cell is covered and all matching crystals are connected.

Is it colourblind-friendly?

Yes. Crystals differ by shape as well as colour, so pairs stay easy to tell apart.