Bridges

Bridges, also known by its Japanese name Hashiwokakero (“Build Bridges”), is a captivating logic puzzle that challenges players to connect a series of islands into a single, unified network using a set of simple but strict rules.

The puzzle is played on a rectangular grid containing scattered “islands”—represented as circles, each marked with a number from 1 to 8. Your task is to draw bridges (straight horizontal or vertical lines) between these islands so that:

• Each island is connected to others by exactly as many bridges as its number indicates.
• No more than two bridges may run directly between any pair of islands.
• Bridges cannot cross other bridges or pass through islands.
• All islands must be part of one continuous, interconnected network—you must be able to travel from any island to any other via bridges.
• Despite its minimalist appearance, Bridges offers deep logical challenges. Solving it requires careful deduction, spatial reasoning, and strategic planning—especially when working with high-numbered islands in tight spaces or ensuring the final layout remains fully connected.

Originally published by the Japanese puzzle company Nikoli, Bridges has become a favorite among logic puzzle enthusiasts worldwide.

Draw horizontal or vertical bridges to link all the islands. Bridges may be single or double; they may not cross; all islands must end up connected to each other; and the number in each island must match the total number of bridges ending at that island (with double bridges counting as two). Note that loops of bridges are permitted.

Click on an island and drag left, right, up, or down to draw a bridge to the next island in that direction. Repeat the action to create a double bridge, and do it once more to remove the bridge if you change your mind. Click on an island without dragging to mark it as completed once you believe you’ve placed all its bridges.

Solving Bridges puzzle relies on logical deduction and a set of consistent strategies. The goal is to connect all islands (numbered circles) with bridges so that:

• Each island has exactly as many bridges as its number indicates.
• Bridges run only horizontally or vertically.
• No more than two bridges can connect any two islands.
• Bridges cannot cross other bridges or islands.
• All islands must be connected into a single continuous network.

Here are the key strategies used to solve Bridges puzzles:

1. Start with High-Numbered Islands (Especially in Corners or Edges)

• Islands with 8 (in a 4-directional grid) must have 2 bridges in each direction—fill them in immediately.
• Islands with 7 must have 2 bridges in three directions and 1 in the remaining—only possible if all four directions are available.
• Corner islands max out at 4 (2 bridges × 2 directions); edge (non-corner) islands max at 6. → If a corner island shows 4, draw 2 bridges in both directions right away.

2. Use the “Only Possible Direction” Rule

• If an island needs N more bridges but only has N valid directions left (e.g., a “3” with only two neighboring islands, one of which can accept 2 bridges), deduce exact placements.
• Example: A “1” with only one neighboring island → must connect to it with a single bridge.

3. Avoid Isolating Islands

• Never draw bridges in a way that cuts off part of the puzzle. All islands must remain reachable.
• After placing bridges, check that no island (or group) is disconnected from the rest.

4. Track Remaining Bridge Needs

• Keep a mental (or penciled) count of how many bridges each island still needs.
• Update this after every placement—this often reveals forced moves.

5. Use the “Two-Bridge Limit” to Block Options

• If two islands already share 2 bridges, no more can be added between them.
• If an island only needs 1 more bridge, it can’t accept a second bridge from any neighbor.

6. Look for “Mutual Dependency” Between Islands

• Example: Two islands each need 2 more bridges, and they only connect to each other and one other island. This often forces a double bridge between them.

7. Work from the Outside In

• Edge and corner islands have fewer connection options, making them easier to resolve early.
• Solving the perimeter often unlocks the center.

8. Ensure Global Connectivity (Final Check)

• Near the end, verify that the entire bridge network is one connected component—no separate “island groups.”