A brief and indirect allusion to a person, place, thing, or idea. Those being referred to are not specified by name or any other identifying information.
Literary allusion:
Definitional allusions in literature, poems, and fairy stories
Historical allusion:
A Glance to the Past: Defined by their associations with past places, people, and events
Perhaps the princess's debating of which door to chose helped create a unclear ending, since she was having a hard time deciding. The author also created two sides equally distributed in details of which door is a better idea. Since you need it quickly I wont look deep into it. Hope this helps