Beat is an open source screenwriting app for macOS and iOS. It uses the Fountain markup language to write screenplays. Fountain is a plain text format, which means that you can open your files almost anywhere, and Beat just formats it as a screenplay (or novel).
Read the comprehensive Fountain articles to get started!
Beat was created by a screenwriter for other screenwriters and tries to stay as distraction-free as possible and let you write in a flow. There are a ton of power user tools available under the hood though, and this documentation covers most of them.
If you have any questions, don’t be afraid to drop in the Beat Discord or e-mail the developer at beat@beat-app.fi!