Here's some things I have made/am making:
Uni Submarine Simulator Thing
All that said, it doesn't actually work.
I needed to learn the notes on the guitar better, because in my 13 long years playing I was always really shit at sight reading and stuff, so I came up with this. Unfortunately I never finished it, and its a bit amateur (all basic JS DOM functions, which is a bit unweildly for this use case). Maybe I'll get back to it some day. There's a working ish version on glitch though.
The idea is you can make annotations as though they were comments on each page of homestuck. Got the idea from a friend on discord and got very fixated on it. Desparately needs a overhaul. I was an amateur when I made it.
Link is dead right now whilst I sort rehosting it.