Been working on Topos for a while now. The idea came from a book I read as a kid called Moonwalking with Einstein, which introduced me to memory palaces. I've used them ever since when trying to retain important information and always thought the technique deserved a proper app for studying.

You scan any room with your iPhone camera and the app maps your physical space using ARKit. You then pin flashcards to specific locations in that space. When you walk through the room later, the cards appear floating where you left them. Your brain builds a spatial map of the information, which is exactly how the memory palace technique is supposed to work.