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/src/board.ts

@@ -372,6 +372,9 @@ export function hasWarpLineOfSight(
     // A filled mouth chokes the tunnel unless the viewer/target IS the mouth.
     if (blockedCells?.[cellKey(mouthA)] && cellKey(from) !== cellKey(mouthA)) continue;
     if (blockedCells?.[cellKey(mouthB)] && cellKey(to) !== cellKey(mouthB)) continue;
+    // A wall built over either mouth seals the tunnel to sight entirely.
+    if (edgeState(board, mouthA, sideA) !== "open") continue;
+    if (edgeState(board, mouthB, w.to.side) !== "open") continue;
 
     // Rotation taking the far board's inward direction onto sideA.
     const u = DIR[inward], v = DIR[sideA];

packages/engine/src/game.ts

@@ -744,6 +744,16 @@ interface DamagePipeline {
   kind: "spell" | "physical";
 }
 
+/** The far mouth of the warp whose near mouth is this edge, if any. */
+function pairedWarpMouth(
+  board: AssembledBoard, cell: Cell, side: Side,
+): { cell: Cell; side: Side } | null {
+  const w = board.warps.find(
+    (w) => cellKey(w.from.cell) === cellKey(cell) && w.from.side === side,
+  );
+  return w ? { cell: w.to.cell, side: w.to.side } : null;
+}
+
 const CARD_EFFECTS: Record<string, AttackEffect | NeutralEffect | CounterEffect> = {
   // --- Attacks: damage ------------------------------------------------------
   fireball: {
@@ -979,7 +989,12 @@ const CARD_EFFECTS: Record<string, AttackEffect | NeutralEffect | CounterEffect>
       if (!cmd.target || cmd.target.kind !== "edge") return "create-wall targets a wall edge";
       const { cell, side } = cmd.target;
       const view = boardView(state);
-      if (!view.cells[cellKey(cell)] || !view.cells[cellKey(neighbor(cell, side))]) {
+      // A board-edge warp mouth counts as a wallable line: bricking over
+      // the opening is a classic play, and the far "space" is the tunnel.
+      const isWarpMouth = view.warps.some(
+        (w) => cellKey(w.from.cell) === cellKey(cell) && w.from.side === side,
+      );
+      if (!view.cells[cellKey(cell)] || (!view.cells[cellKey(neighbor(cell, side))] && !isWarpMouth)) {
         return "walls must be created between two spaces on the board";
       }
       const key = edgeKey(cell, side);
@@ -988,6 +1003,14 @@ const CARD_EFFECTS: Record<string, AttackEffect | NeutralEffect | CounterEffect>
       state.edgeOverrides[key] = "wall";
       state.createdEdges[key] = true;
       events.push({ type: "wallCreated", caster: caster.id, edge: { cell, side } });
+      // A warp is ONE tunnel: bricking a mouth walls both ends.
+      const pair = pairedWarpMouth(view, cell, side);
+      if (pair) {
+        const pkey = edgeKey(pair.cell, pair.side);
+        state.edgeOverrides[pkey] = "wall";
+        state.createdEdges[pkey] = true;
+        events.push({ type: "wallCreated", caster: caster.id, edge: pair });
+      }
       return null;
     },
   },
@@ -1005,6 +1028,13 @@ const CARD_EFFECTS: Record<string, AttackEffect | NeutralEffect | CounterEffect>
       delete state.doorStates[key];
       delete state.createdEdges[key];
       events.push({ type: "wallDestroyed", caster: caster.id, edge: { cell, side }, wasDoor: current === "door" });
+      const pair = pairedWarpMouth(view, cell, side);
+      if (pair && state.createdEdges[edgeKey(pair.cell, pair.side)]) {
+        const pkey = edgeKey(pair.cell, pair.side);
+        state.edgeOverrides[pkey] = "open";
+        delete state.createdEdges[pkey];
+        events.push({ type: "wallDestroyed", caster: caster.id, edge: pair, wasDoor: false });
+      }
       for (const c of [cell, neighbor(cell, side)]) {
         for (const p of state.players) {
           if (p.alive && cellKey(p.position) === cellKey(c)) {