How to Solve Island Bridges: Logic Puzzle Strategy
Island Bridges is pure logic. Every island needs exactly as many bridges as its number, bridges run straight, you can build one or two between a pair, they never cross, and every island must join one network. Levels always have a solution, and the right deductions solve them without guessing.
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Start with forced islands
Count each island's neighbours. Each neighbour can take at most two bridges, so an island with a 4 in a corner, with only two neighbours, needs double bridges to both. An 8 needs double bridges in all four directions. A 6 with three neighbours also needs doubles to all three. Build these first.
Use the near-forced rule
If an island needs one less than its maximum, every neighbour must still get at least one bridge. For example, a 3 with two neighbours must have at least one bridge to each, and a 5 with three neighbours the same. Place those single bridges right away; you can add the doubles later as other clues fill in.
Smaller numbers give clues too. A 1 or 2 island with only one neighbour must send all its bridges there. And once an island is satisfied, every neighbour loses that island as an option, which often forces the next move somewhere else on the board.
Avoid isolated groups
All islands must end up in one network. Two 1s next to each other can never be joined, because they would form a closed pair. In the same way, two 2s cannot be joined by a double bridge. As the puzzle fills in, watch for any group that is about to be completed on its own and make sure it still has a way out.
Use the no-crossing rule
Bridges cannot cross, so a bridge you build can block the only route to another island. When an island has only one possible neighbour left because other bridges cut it off, the remaining bridges must go there. Look for these blocked routes when you feel stuck.
Score well
Each level earns 100 points per level number, plus a speed bonus, minus a little for each hint. Satisfied islands turn green, which makes it easy to see what is left. Undo is there for mistakes, and solving level 15 or higher without hints or undo earns the Master Engineer achievement.
Questions
- How many bridges can join two islands?
- One or two, never more, and they must run in a straight line.
- Can two 1 islands be joined?
- No. They would form a closed group cut off from the rest of the network.
- How do I know an island is finished?
- It turns green when it has exactly as many bridges as its number.
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