This page runs Quill, a web app for playing and tinkering with Ink stories. (Ink is a mini-language for writing choose-your-own-adventure games.)
When you click Play, your Ink story will appear on the right and become playable. You can test out (and modify) the example snippets below, or play the short-but-complete Ink story The Intercept. If you're experimenting, the Ink tutorial may come in handy.
If you are playing a story and making revisions as you go along, you can use Play Ink (Replay Choices) to replay your previous path on the latest revision.