We’ve all been in this situation. You’re in a library looking for a book. You get the reference from the catalogue, but the book is not on the shelf. You check again and see the book is definitely in the library. Some bastard’s maliciously mis-shelved it. Now thanks, to a tip from Why, That’s Delightful, you can express your bibliographic rage via this game from Carnegie Mellon.
Pick up the books from the table and put them IN THE CORRECT PLACES on the shelves. It’s hours of carefully catalogued bliss.