How to solve Bridges
Count each island’s neighbors. Start where the number leaves no choice, then let every full island close off its unused sides.
How it works
Bridges gives you islands with numbers. You join them with bridges that run straight across or straight down. Each number says exactly how many bridges touch that island. Two islands can share one bridge or two, never more. Bridges can’t cross each other or pass over an island.
One more rule ties it together: at the end, every island must be part of one connected network. You can walk from any island to any other along bridges.
The main move is counting. An island’s neighbors are the nearest islands straight up, down, left and right. Each can take at most two bridges, and fewer if its own number is small or it is already full. If the number needs every bridge the neighbors can give, draw them all.
Where to look first
Big numbers with few neighbors and small numbers with one neighbor give the first bridges. Islands in corners and along edges have fewer neighbors, so start there.
After every bridge, look at both ends. An island that just became full closes its other sides, and its neighbors may now have no choice.
Keep the network in one piece
Never join two islands so that a group ends up full but cut off from the rest. Two 1s can’t share a bridge unless they are the only islands. The lesson on isolation shows how to use this.
Worth memorizing
Count neighbors, then count bridges.
Each neighbor gives at most two.
A full island closes its other sides.
Look at its neighbors next.
No full group may be cut off.
Every island joins one network.
Practice
0 of 4 rightOn the empty map, which of these islands can you finish right away?
The 6 is done. Where can the 2 at the bottom right send its bridges?
How many more bridges does the 5 need?
Which island can the 1 connect to?