Patch

flask/game.py

@@ -118,6 +118,9 @@ def push(data, ws):
             db.session.rollback()
             raise AssertionError("you can't push objects into wall.")
         current = objects[y][x]
+        if current is not None and current.get("type", None) == "book":
+            db.session.rollback()
+            raise AssertionError("you can't push objects into books.")
         objects[y][x] = last
         if current is None:
             ok = True