In a camera obscura the outside world appears upside down on a dark wall. Tradition reads it as seeing reality from an unusual angle and the mind as a darkened room.
When this appeared in your dream, what were you feeling?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.