Sluice: a sliding pipe puzzle

Sluice is a puzzle about moving whole lines at once. The board is a grid of pipes, and around its edge sit a tap and a handful of flowers. You never turn a pipe in Sluice. Instead you drag an entire row or column, and it slides as one piece, wrapping around so that whatever falls off one edge reappears at the other. Water runs out from the tap through every pipe that happens to line up, and a flower stays a closed bud until the water actually reaches it. Open every flower and the level is done.

The catch, and the whole pleasure of it, is that rows and columns cross. Slide a row to fix one corner and you have just moved a tile out of five different columns. Nothing here can be solved a piece at a time.

How to play

Drag any row sideways or any column up and down. The lane moves as a unit and wraps around the board. Water spreads from the tap the instant the pipes line up, lighting them blue as it goes, so you can see how far you have got at every moment.

• Slide: drag a row left or right, or a column up and down. Whatever leaves one edge comes back in at the opposite edge.
• Follow the water: pipes carrying water turn blue and dry pipes stay grey, so the blue is a live measure of progress.
• Open every flower: a flower blooms the moment water reaches it. Open them all to finish the level.
• Undo, Restart, Hint: step back, reset the board, or ask for a move. Hint does not just point at a lane, it plays a full sequence for you.

Your progress saves automatically, so you always return to the level you left off on. There is no move limit and no timer.

Why it is clever

Two things make Sluice different from an ordinary pipe puzzle.

The first is that every board has exactly one solution. Each level is checked at generation by searching the whole neighbourhood around the scramble, and any board with a second arrangement that also waters every flower is thrown away and regenerated. So when you find the answer, it is the answer, and there was no luckier route you happened to miss.

The second is the technique hiding inside the rules. Because a row and a column cross at exactly one square, you can slide a row, slide a column, then undo each in turn, and the board comes back almost unchanged: exactly three tiles have moved and everything else is untouched. That is what lets you repair one corner without wrecking the rest, and it is the same idea a Rubik's cube rests on. It is not obvious, so the Hint button demonstrates it rather than describing it. Watch it once and you have the tool for every level after.

Tips

• Get the pipe next to the tap facing the tap first. Until it does, nothing on the board is wet and you are working blind.
• Use the blue, not the flowers. Flowers only open at the very end of a chain, but the spread of blue tells you whether a slide helped.
• When a slide fixes one thing and breaks another, that is the moment to reach for a three tile sequence instead.
• Press Hint when you are stuck rather than when you are lost. Watching what it does with a board you already understand is how the technique sticks.

Frequently asked questions

Is Sluice free? Yes, completely free to play, with no account and no download, in any modern browser on phone, tablet or desktop.

Does it work on mobile? Yes. Sliding a lane with your thumb is the natural way to play it, and the board grows to fill a phone screen.

How is it different from Bloom? Bloom has you rotate one pipe at a time. Sluice never rotates anything. You move whole rows and columns, which makes it a very different and considerably harder puzzle.

How do I win? Slide rows and columns until water runs from the tap to every flower on the edge of the board.

Is every level solvable? Yes. Every board is built from a working pipe network and then scrambled by sliding, and a slide is always undone by another slide, so the way back always exists.

Enjoy a good thinking puzzle? Try Bloom, Fold or Untangle, or browse all Zamborin games.