What are the rules of the Pipes Puzzle?
Every tile holds a piece of pipe: an end, a straight, a bend, a T or a cross. Turn the tiles until all the pipes join into one network that reaches every tile. Every pipe must meet a pipe on the next tile, none may point off the board, and the network has no loops. Each puzzle has exactly one answer, so every tile has one right position.
Choose a 5 × 5, 7 × 7 or 9 × 9 grid (5 × 5 is picked to begin with). Tap a tile to turn it a quarter clockwise; right-click it, or hold it on a touchscreen, to turn it back. On a keyboard, the arrows move, Enter turns and Shift with Enter turns back. Tiles joined to the middle tile are drawn darker, so you can watch the network grow.
How do you solve the Pipes Puzzle?
- Start at the edges. No pipe can point off the board, so a bend in a corner has only one position, and a straight or a T on an edge has only one way to lie.
- Keep ends apart. Two ends pointing at each other would make a network of two tiles, cut off from the rest, so they never join.
- Never close a loop. The network has none, so a turn that would close one is wrong.
- Work inwards from what is certain. Each settled tile tells its neighbours whether a pipe must, or must not, come their way.
How is your Pipes Puzzle result calculated?
Your result is the number of turns you made, each quarter turn either way counting one, until every tile is joined. It is set against the fewest turns that solve your board. Because the puzzle has one answer, that is exact: for each tile, the shorter way round from where it starts to where it must end, added up. No tile needs more than two turns, a straight looks the same after a half turn, and a cross after any turn. A hint turns one tile the short way into place for you, and those turns count like yours, so a hint never improves a result. Your hints and time are shown beside it.
What does my Pipes rating mean?
The rating compares your turns with the fewest for your board, so it needs no averages: exactly the fewest is Perfect, up to 15% more is Excellent, up to 35% more is Good, and up to 80% more is Fair. Each board has its own fewest; for example:
| Rating (turns) | Fewest 20 | Fewest 40 | Fewest 70 |
|---|---|---|---|
| Perfect | 20 | 40 | 70 |
| Excellent | 21–23 | 41–46 | 71–80 |
| Good | 24–27 | 47–54 | 81–94 |
| Fair | 28–36 | 55–72 | 95–126 |
| Keep trying | 37+ | 73+ | 127+ |
Does every Pipes Puzzle here have exactly one answer?
Yes. Each puzzle is made in your browser when you press Start. The answer is a random network spanning the grid, with no loops; a separate search then tries every way to turn the tiles, and the network is kept only if exactly one way joins it all up. Then every tile is turned to a random position. The site's tests check the search against trying every position on small boards, and make puzzles of every size.
Where does the Pipes Puzzle come from?
Pipe-turning puzzles have many names. Simon Tatham's Portable Puzzle Collection calls the same idea Net, with the network growing from the middle as it does here. For another board where every move changes what you see, try Lights Out; for paths you draw yourself, try Number Link.