Hashiwokakero 橋をかけろ
Hashiwokakero (Bridges, Hashi) connects numbered islands with bridges. Each island must have as many bridge connections as its number. Bridges cannot cross; at most two between any pair. Graph-theory elegant.
Rules
Island numbers 1–8. Draw horizontal or vertical bridges between islands. Each island's total bridge count must equal its number. Between any pair: 0, 1, or 2 bridges; no crossing; bridges do not pass through islands. All islands must form one connected network. Solve by logic; unique solution. Island of 1 adjacent to only one other forces one bridge; island of 8 needs two bridges in every direction; use connectivity to eliminate disconnected subgraphs. Graph-theory elegant.
History
Hashiwokakero appeared in Nikoli in 1990. "Bridges" and "Hashi" are common English names. NP-complete puzzle class. Major export to Western puzzle books and apps such as Conceptis Hashi and Simon Tatham's Portable Puzzle Collection. The bridges metaphor and clean constraints make it popular worldwide.
Tips for beginners
Start with highest-numbered islands—fewest options. Ensure every island can connect to the main network; avoid isolated groups. Two bridges between close islands early can block later paths—be conservative initially.
Cultural context
Strong Western puzzle book presence; dedicated Hashi apps. Puzzle mathematics: solvability is NP-complete. Bridges metaphor resonates globally. Hashiwokakero (Bridges) connects numbered islands; each island needs as many bridges as its number. The graph-theory elegance and clean constraints make it popular worldwide. Available on Nikoli.com, Conceptis Hashi, and Simon Tatham's Portable Puzzle Collection.
Play online
Play at Nikoli.com, Conceptis Hashi (conceptispuzzles.com), Simon Tatham's Portable Puzzle Collection, Puzzle-Nonograms.com. Mobile: Conceptis Hashi app.
Where to Buy or Play
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- 📖 Hashi / Bridges Puzzle Book (Nikoli) Official Nikoli hashiwokakero collection
- 📱 Play Hashi free in browser (Simon Tatham — Bridges) Free, open-source browser implementation with adjustable grid size