The rules
The grid has islands with numbers from 1 to 8.
- Connect islands with straight bridges, horizontal or vertical.
- Two islands share one or two bridges at most.
- Bridges never cross and never pass over an island.
- The number on each island is how many bridges leave it.
- In the end, every island is connected into one network.
Every puzzle has exactly one solution, and you reach it by logic, without guessing.
How to play here
- Click the space between two islands to add a bridge. A second click doubles it, a third removes it.
- Keyboard: the arrows move between islands. Shift with an arrow adds a bridge in that direction.
- An island with all its bridges gets an inner ring. An island with too many is outlined with a dashed line.
Difficulty levels
| Level | Size | What it takes |
|---|---|---|
| Easy | 7×7 | Counting |
| Medium | 9×9 | + Crossing |
| Hard | 11×11 | + Isolation, once |
| Expert | 13×13 | + Isolation, twice or more |
Techniques
Counting
An island showing 4 with only two neighbors needs a double bridge to each. An island showing 3 with two neighbors needs at least one bridge to each. In general: each neighbor must get whatever the other neighbors can’t provide. And once an island is full, it gets no more bridges.
Crossing
A bridge that must exist blocks any bridge that would cross it. This often opens up new counting.
Isolation
Two islands showing 1 can’t connect to each other, because they would be closed off alone. Two islands showing 2 can’t share a double bridge. In general: never close off a group of full islands cut off from the rest of the grid.
Tips
- Start with islands in the corners and islands with big numbers. They have the fewest options.
- After each bridge you add, check what changed for the neighbors.
- Think about the whole grid: is there an area at risk of being cut off?