Lark is a free download in the iTunes app store.
It's currently available in the US, Canadian, Australian, New Zealand, United Kingdom, and Irish app store with more countries added soon.
Lark is optimized for iOS 7+ and is compatible with iPhone 4s, iPhone 5, iPhone 5s, iPhone 6, iPhone 6+, and iPod Touch. It is not available for iPad or Android devices. (Although you can download it onto your iPad and double-up resolution).
Separately, our web-based poetry app at Storybird is optimized for Chrome, Safari, and IE browsers and will work on tablets and phones.