Stepmania is great. I actually built a skeleton of a workout tracker for DDR a while back using the simfiles I was already playing this on. I haven't had a space to play in that consistently in years, though, so I never bothered to bring the hosted demo back up when Heroku killed their free tier and kinda stalled the development before it got more than just fleshed out enough to be kind of useful.

That said, there's a mostly working .sm to .ssc converter (it's still got a couple edge cases around punctuation in titles), as I had to migrate the simfiles to something with named properties anyway to get reliable data out of them.

This, and the seeder script (which I wrote using a bunch of fetch requests in order to also test a bunch of my frontend logic, before Node started shipping with that) that I used to seed all the DDR arcade tracks into a db, were actually my first experience with Deno. It's been my go-to experiment tool pretty much ever since.

If anyone's curious, it's under my github (same username) at step-step-recollection. (And ...recollection-scripts, and ...recollection-ui. Annoyingly I never got to experimenting with server-side rendering on it, so that's also a separate repo.)