The Hey Dad app scans images included in "Hey Dad - What's the Tallest Building?" book and then displays fun 3d models and animations on top of the images! Your kids will love how this brings the book to life! Just open the Hey Dad app and hold your device over the pages of the book, the stunning animated images will come alive right before your eyes. Buildings will pop out of the pages, characters will move, and clock hands will spin. You can also visit our website - heydadstories.com and download the book for free to use with this app.