PlankwayReefs: the Plankway twist on the bridges puzzle
Classic bridges puzzles only have islands and water. Plankway adds reefs: rocks in the water that a bridge can never cross. They look like a small detail, but they change how you read the board.
What a reef does
A reef occupies one water cell. A bridge that would pass over that cell cannot be built, so two islands on either side of a reef cannot connect, even though they are in a straight line. A bridge that passes next to a reef, in another row or column, is fine.
Here the reef settles everything: each 1 must connect downwards, and the two 2s connect along the bottom.
Fewer neighbours, more certainty
Every blocked neighbour means fewer places for an island’s bridges to go. That makes the counting techniques kick in sooner. A 4 that would normally have three neighbours, but has one of them blocked by a reef, needs a double bridge to both others.
Reading the board with reefs
- Before you count an island’s neighbours, check the lines between them for reefs. The most common mistake is counting a neighbour that is not really there.
- Reefs also block chains: an island behind a reef is not visible, but the next island along the same line is not visible either, because a bridge always connects to the nearest island.
- Use reefs as walls for whole regions. A part of the board surrounded by reefs and the edge has few exits, which is where the only way out comes in.
Reefs are placed by the generator after the island network is built, only where they keep the puzzle uniquely solvable. Mondays have two, Sundays up to five. In the archive every puzzle shows in how many steps a reef played a role.