Repudo. What does it cost to create an interactive app? Want to build a mobile app? Here's how to convince the CFO. An Ex-Pixar Designer Creates Astounding Kids' Book On iPad. E-books are already a fraught subject for many readers, writers, publishers and designers, but children's e-books are even more so. Is it rotting their minds? Is it as good as good ol' paper? Is it too interactive for their own good? Obviously there are no practical answers to such questions, but at least one children's e-book/app/thingie (what do we call these things, again?) Is doing it very, very right. Clash : Rise of Heroes.