Requires Node.js (16 or later), Python (2 or 3), and Java. It is known to work in these environments but should work in many others:
Install dependencies:
npm ci
Open tests/vertical_playground.html in a browser for development. You don’t need to rebuild compressed versions for most changes. Open tests/vertical_playground_compressed.html instead to test if the compressed versions built properly.
To re-build compressed versions, run:
npm run prepublish
scratch-gui development server must be restarted to update linked scratch-blocks.