Flow

How to Play Flow (Numberlink)

Flow — also known as Numberlink (ナンバーリンク) — is a path-connection puzzle. The grid holds several pairs of coloured dots. Your job is to draw a pipe joining each pair, so that the pipes never cross and every single cell of the grid is filled. Drag from one coloured dot, through orthogonally adjacent cells, to its matching dot. A path can turn but never crosses itself or another colour; if you draw over an existing pipe, that pipe is cleared back to its dots, so you can always redraw. You win the instant every pair is connected AND the whole board is covered. Every puzzle here has exactly one full solution, so there is a single correct way to fill the grid.

Solving Techniques

• Follow the walls and corners: A dot in a corner has only two ways out, and a dot on an edge is tightly constrained. Start there — often the first few cells of a corner path are forced.
• Fill every cell: Because the whole grid must be covered, an empty cell trapped in a pocket must belong to whichever colour can still reach it. Spotting cells that only one colour can fill unlocks the rest.
• Don't waste space: A pipe that wanders and doubles back usually steals cells another colour needs. Prefer the most direct route unless a longer one is forced to cover an otherwise stranded cell.
• Avoid the self-touch trap: Two parts of the same pipe running side by side is legal but almost always wrong here — it wastes a cell and blocks a neighbour. Keep each colour a clean, non-touching line.
• Work the parity of tight regions: In a narrow channel or a 2-wide strip, count the cells each colour must take. If the counts don't add up, a route is wrong — back it out and try the other turn.

How do you solve Flow faster? Anchor the corners and edges first, then connect the pairs that have the fewest possible routes, always keeping an eye on which cells remain uncovered. Because every board has a single full covering, a completed grid with all pairs joined is guaranteed correct — the leaderboard ranks solves by completion time, so the cleanest, most direct set of paths wins.