Comment by ForceBru
I thought it should be extremely portable ("everything just works, it's native"), but it doesn't work on iOS 9.3.6. It doesn't even let me input text into the textarea...
A natural extension seems to be a source code editor with syntax highlighting, like those used in https://marimo.io/, Jupyter, https://plutojl.org/ and other notebook-like Web editors.
I'm not sure why you are testing in iOS 9.3.6. (which was released in 2015), when the documentation says support for Safari is for versions 16 and above.