Y
Y — starting position
Invented by Claude Shannon and Craige Schensted in the 1950s. Played on a triangular board of hexagonal cells. Two players alternate placing stones. The first player to form a connected group touching all three edges of the triangle wins.
Board
A triangular grid of hexagonal cells. Standard sizes range from side-length 9 to 15. Each edge of the triangle is one “side” — there are three sides total.
Corner cells touch two edges simultaneously.
Setup
The board starts empty. Black plays first.
Rules
- Players alternate placing one stone of their colour on any empty cell
- Stones never move or are captured once placed
- The first player to form a single connected group of their stones that touches all three edges wins
- The swap rule applies: after Black’s first move, White may choose to swap colours instead of placing a stone
Key Differences from Hex
| Concept | Hex | Y |
|---|---|---|
| Board shape | Rhombus/parallelogram | Equilateral triangle |
| Edges | 4 (2 per player) | 3 (shared) |
| Win condition | Connect YOUR 2 opposite edges | Connect ALL 3 edges |
| Corner ownership | Corners belong to one player’s edges | Corners touch 2 edges (valuable) |
| Draw possibility | Impossible (Hex property) | Impossible (same topological guarantee) |
Why This Tests the Engine
Y generalises the connection-win mechanic from “2 edges, each owned by a player” to “3 edges, first to touch all three”. The engine’s hasPath() traversal needs to detect multi-target connectivity — not just “does a path exist from edge A to edge B” but “does a single group touch edges A AND B AND C”.
The topology must support a triangular hex grid (not just hexagonal or rhombus). The win-detection rule must be parametric over edge count, not hardcoded to 2.