Footbridges

Hard Footbridges puzzles

Hard puzzles are 9×9 and 10×10 with 15 to 24 islands, and need you to look at whole groups: when a group has only one way left to reach the other islands, or an island would close off its neighbors by taking all its bridges from them, a bridge has to go somewhere else.

Practice gives you puzzles you haven't solved yet, as many as you like, and keeps your best time without hints. Every puzzle has exactly one solution and can be solved by logic alone.

How to play Footbridges

1. Every island's number is how many bridges it has.
2. Bridges run straight across or down, between two islands with only water between them.
3. Two islands can be joined by one bridge or two, never more.
4. Bridges can't cross each other.
5. In the end, all the islands are joined into one group.

Drag from an island toward a neighbor to build a bridge, and do it again for a second one. A third time takes them away. Tapping the water between two islands works too. An island lights up once it has all its bridges. On a keyboard, use the arrow keys to move between islands, Shift and an arrow to build that way, and Ctrl+Z to undo.

Solving tips

• Start with the big numbers. A 4 in a corner, a 6 on an edge or an 8 anywhere needs two bridges to every neighbor.
• Count what's left. A 3 with only two neighbors needs at least one bridge to each of them, and a 5 with three neighbors does too.
• Don't close a group off. Two 1s can't be joined to each other, and two 2s can't be joined by two bridges: they'd be finished, with no way left to reach the other islands.
• Keep a way out. When a group of islands has only one link left to the rest, that link needs a bridge.