A koan is a riddle that cannot be solved by logic alone. In a dream it is read as a problem that asks you to stop forcing an answer and see it from an entirely different angle.
Where in your waking life have you met something like this lately?
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.