Pipes Logic Puzzle

Pipes is a pipe-connecting puzzle. Each cell is a tile with openings to the north, east, south, or west. You rotate the tiles so the openings meet. The grid is finished when the pipes form one tree. You can play squares from 5×5 to 10×10, plus 7×9 and 6×8, in easy, medium, and hard. Every puzzle here has exactly one solution.

Rules

The board is a grid of pipe tiles. A tile keeps its shape. You only turn it. An end has one opening. A straight has two opposite openings. A corner has two openings that meet. A tee has three openings.

Two tiles meet when each opens toward the other. An opening that runs off the board is a loose end. An opening that faces a neighbour which does not open back is a loose end too.

The finished grid is one tree. Every tile is connected to the others, there is no loop, and there is no loose end. Pipes do not wrap around the edges.

A lock is your own mark. It freezes a tile so a tap does not turn it. The puzzle does not start with locks.

While you play, an unlocked loose end stays quiet. Tiles on a loop are marked, locked or not. A locked opening that leaves the board, two locked neighbours that disagree, and a locked group that cannot grow to fill the board are marked too.

The puzzle is solved when the pipes are one tree and the check is clean.

Controls

Choose Rotate or Lock under the board. Rotate is the start. The tool stays until you pick the other one. A tap does not switch tools.

In Rotate, tap a tile to turn it clockwise a quarter turn. Hold the tile, or right-click it, to turn it the other way. The right-click menu stays closed. A drag that leaves the tile does not rotate it or its neighbours.

In Lock, tap a tile to freeze it, and tap again to unlock it. Hold or right-click still turns an unlocked tile the other way.

The arrow keys move a cell cursor. The first arrow selects the top-left cell and does not turn it. A turns the selected tile counter-clockwise. D turns it clockwise. F turns it halfway, and undo steps one quarter at a time. S toggles the lock. The keys 1 and 2 select Rotate and Lock.

Press Hint for one step the pipes already force, with a sentence saying why. The hint highlights the cells it uses, then applies the turn or the lock. Press Check when you want the board checked against the rules. Undo and Redo step through your turns and locks, and Reset returns every tile to the start. When the tree is complete, the pipes turn teal.

A coral pipe is a loop, or another break that is already visible, on a tile the rules flag. The size and difficulty menus list the 24 bands that ship. The daily puzzle is 7×7 easy.

Techniques

Easy:

• border-close: A side that would leave the board is closed. That side of the tile is already fixed.
• agree-edge: Every remaining turn of this tile agrees on this side, so the side is fixed.
• single-orient: Only one turn of this tile is still possible.

Medium:

• already-linked: These two tiles are already connected, so this side must stay closed or it would loop.

Hard:

• arm-loop: This turn would join two pipes that already meet, so that turn is impossible.
• component-trap: Every open end of this turn runs into a group that is too small to cover the board.
• dead-end-bound: Coming this way can reach only a limited group of tiles.
• component-chain: A trap and a bound both apply, so the tile is fixed by that pair of limits.

Beginner tips

Start with a tile on the edge. Any opening that would leave the board is closed, so that tile has fewer turns left. When only one turn remains, lock it.

A loop is already wrong. Turn one of its tiles, or undo back to the step that closed the cycle. An unlocked loose end can wait. It is not a mark until the pipes fail to meet.

If you are new to Pipes, start with a 5×5 easy grid, or the daily 7×7 easy grid, and move up once turning feels natural. Play runs from Easy → Hard on 5×5 through 10×10, and on 7×9 and 6×8.