The Good: Petting Zoo contains uniquely hand-drawn animations and has a minimalistic, intuitive interface. The Bad: At $1.99, Petting Zoo is pricey for an app that will never receive additional chapters. The Bottom Line: Petting Zoo is a quirky and absolutely charming app, but because it's structured more like a picture book, pass it up if you're looking for a traditional level-intensive game. Christoph Niemann, a visual columnist at The New York Times and an illustrator whose works appeared on the cover of several magazines covers including The New Yorker and Wired, launched an iOS app recently called Petting Zoo. For kids, but has wide appeal Aimed toward children ages 4 and up, this app is categorized under games, but it's more of an interactive picture book than anything else. Each drawing constitutes as a chapter, but there is no overall narrative story that takes place. Instead, it simply contains 21 of Niemann's hand-drawn animals that each react in different ways to five swipe movements (up, down, left, right, and center tap)."Nothing is computer generated," Niemann told CNET. "Essentially, the feeling I wanted to create was a simple drawing that the moment you put your finger on it, something happened that was surprising and fun."And it certainly is surprising. Though not meant to hold an adult's attention for long, Petting Zoo has a handful of moments that made me actually chuckle out loud. It's more than just blowing a lion's mane from side to side (though there is that). The first time you go through it, you never know what an animal's reaction will be. And often, the results can be delightful.For instance, there are animals that turn into musical instruments, a butterfly that holds its own against a cat, and a break-dancing Dachshund that if you aren't even remotely tickled by the way its small elbows look while it's doing "the worm," proves you have a heart of stone. Keeping the user experience simple These succinct visual punchlines are not without work, however. From its conceptualization to its release, the app took about a year to complete. For every animal (or "chapter") included in the app, Niemann estimates that there were at least seven or eight movements and actions that were scrapped. In that same vein, these animals had at least three fully animated, but ultimately rejected, sequences under their belts.