About Flow Link

Flow Link is a path-routing puzzle that adds a connectivity requirement to the classic color-matching format: every matching node pair must be connected, AND every cell in the grid must be part of some path — with no isolated regions permitted. This dual constraint — connect all pairs AND fill all cells — creates a much harder planning challenge than either constraint alone, as routes that solve the connectivity easily often leave isolated cell clusters that cannot be filled without disconnecting other pairs. The puzzle class is NP-complete for arbitrary grid sizes, meaning there is no known efficient algorithm for solving it, though human intuition often finds solutions quickly through pattern recognition.