A warp mouth is a wallable line — and the tunnel seals whole

Create Wall refused the board-edge openings: no far cell, so "walls
must be created between two spaces". But bricking over a lettered
opening is a classic play, and the far space is the tunnel itself.
A warp mouth now counts as wallable — with the wall raised at BOTH
mouths, since a tunnel has one passage: no walking in from the far
board, no warp sight through a sealed pair, and tearing down either
end reopens both. The client grows edge hitboxes at the perimeter
mouths so the line is clickable at all.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/engine/test/board.test.ts

@@ -9,7 +9,7 @@ import {
   type SectorPlacement,
 } from "../src/board";
 import { buildDeck } from "../src/cards";
-import { activePlayer, applyCommand, createGame } from "../src/game";
+import { activePlayer, applyCommand, boardView, createGame, gameLos } from "../src/game";
 import { createRng } from "../src/rng";
 import { setupBoard } from "../src/setups";
 import { giveCard } from "./helpers";
@@ -240,3 +240,42 @@ describe("the aisle warp treats its corner as adjacent — sight included", () =
     expect(offAxis).toBeGreaterThan(0);
   });
 });
+
+describe("bricking over a warp mouth", () => {
+  it("create wall seals a lettered opening: no passage, no sight", () => {
+    let { state } = createGame({ playerIds: ["a", "b"], seed: 42, sets: ["basic"], deckRev: 18 });
+    // round 1 passes
+    for (let i = 0; i < 2; i++) {
+      const r = applyCommand(state, activePlayer(state).id, { type: "endTurn", draw: 0 });
+      if (!r.ok) throw new Error(r.error);
+      state = r.state;
+    }
+    const w = state.board.warps[0]!;
+    const caster = activePlayer(state);
+    caster.position = { ...w.from.cell };
+    caster.hand[0] = { instanceId: "cw#1", cardId: "create-wall" };
+    const r = applyCommand(state, caster.id, {
+      type: "cast", instanceId: "cw#1",
+      target: { kind: "edge", cell: w.from.cell, side: w.from.side },
+    });
+    if (!r.ok) throw new Error(r.error);
+    state = r.state;
+    // Passage: stepping into the warp is now a wall.
+    const step = stepTarget(boardView(state), w.from.cell, w.from.side);
+    expect(step.kind).toBe("blocked");
+    // Sight: the far mouth no longer carries warp sight.
+    expect(gameLos(state, w.from.cell, w.to.cell)).toBe(false);
+    // One tunnel: the FAR mouth is walled too, and unwalling it reopens both.
+    const farStep = stepTarget(boardView(state), w.to.cell, w.to.side);
+    expect(farStep.kind).toBe("blocked");
+    const caster2 = activePlayer(state);
+    caster2.position = { ...w.to.cell };
+    caster2.hand[0] = { instanceId: "dw#1", cardId: "destroy-wall" };
+    const r2 = applyCommand(state, caster2.id, {
+      type: "cast", instanceId: "dw#1",
+      target: { kind: "edge", cell: w.to.cell, side: w.to.side },
+    });
+    if (!r2.ok) throw new Error(r2.error);
+    expect(stepTarget(boardView(r2.state), w.from.cell, w.from.side).kind).toBe("warp");
+  });
+});