Sorry for the giant desktop screenshot there, but I’m sure that’s how it’s meant to be used. It’s an information and interactivity dense experience.
But when you need to play and experiment, it’s great! It’s a decent little code editor (Monaco, it seems), it allows you to test whatever sort of HTTP requests you want against it along with a UI for adjusting headers. It outputs logs and gives you a full-on preview for visual things. But I think my favorite thing is how it’s got a straight-up Chromium DevTools jacked right into the UI. Must be because Workers run on V8 just like Chromium does.