We have an app for that!
Mac users can download Mac Script or Mac Shots to streamline their offline experience.
The Celtx Script is lightweight and lightning quick, with just the features you need to optimize your scriptwriting pleasure. Make it full screen and you can write without distraction. Sync with your Online Studio and your mobile app, or save locally and upload to the cloud later!
Celtx Shots is the first app with both storyboarding and set blocking built-in. Shots syncs with Celtx online studio and Celtx Shots on the iPad/iPhone, so you can create anytime, anywhere.
There are currently no PC/Windows or Linux offline apps.