Playground for bikeshedding the topic token?

[bogdanbiv]

The Record & Tuple proposal have used a playground page to make their proposal playable in the browser.
As I understand things, their playground transpiles users' script to currently supported syntax (polyfill) in the browser,
SRC: https://rickbutton.github.io/record-tuple-playground/,

Would this work for picking the token? I mean would it add value to trying characters combos?
Instead of the Syntax Type dropdown in the UI, have a text input that makes some initial validations??? and replaces the topic token throughout the source - if we get to errors we know outright what's the holdup.

The proper playground itself (from the records proposal): https://rickbutton.github.io/record-tuple-playground/#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