1 files changed, 4 insertions, 2 deletions
diff --git a/src/engine/entities/FunctionApplication.ts b/src/engine/entities/FunctionApplication.ts
index bd88bda..ac07f88 100644
--- a/src/engine/entities/FunctionApplication.ts
+++ b/src/engine/entities/FunctionApplication.ts
@@ -30,8 +30,9 @@ import {
   interpret,
 } from "../../interpreter";
 
-const APPLICATION_RESULTS: Record<string, (gridPosition: Coord2D) => Entity> = {
+const APPLICATION_RESULTS: Record<string, (gridPosition: Coord2D) => null | Entity> = {
   _KEY: (gridPosition: Coord2D) => new Key(gridPosition),
+  _EMPTY: (_gridPosition: Coord2D) => null,
 };
 
 export class FunctionApplication extends Entity {
@@ -177,7 +178,8 @@ export class FunctionApplication extends Entity {
       const { name } = data;
       const entityFactory = APPLICATION_RESULTS[name];
       if (entityFactory) {
-        game.addEntity(entityFactory(nextPosition));
+        const entity = entityFactory(nextPosition)
+        entity && game.addEntity(entity);
       }
     }