Update NOTES, ping server, use `self`
- Set up a 30s interval ping back to the server (from the client) to let it know you're still there
- Use `self` instead of `that` for context-passing
- Update NOTES with some details on what to work on next, and clarify some animations and stuff.
- Tweak some marker CSS (but will probably replace these markers entirely, I don't love them)