Looks like a personal Notion, or Obsidian.

I would call this a note-taking app rather than a notebook, which to many mean computational notebooks like Jupyter.

Thanks for the input.

We took inspiration from analog notebooks as a tool for thought, but wanted something for multi-media. We also see NotebookLM as the closest mainstream product to Surf.

Related -- some people who have seen Surf's Applets feature have also called Surf "Jupyter for normies".

More on Surflets: https://github.com/deta/surf/blob/main/docs/SURFLETS.md