The
new DTI is completely flash free, but I don't know really anything about how it works under the hood. Good news is that it's completely open source, so you can probably figure some stuff out by looking through the
github repo. And actually from looking at the README, looks like it's React-based, which I would nooooooot be able to help with (I keep telling myself I'm going to learn some React basics and then running away).
The old DTI is also on github,
here if you want to take a look.
My browser visual experience is mostly limited to
canvas, and with that, mostly limited to
p5js. It seems like there have been a
couple dressup games made with it (well, probably more, but I'm not gonna dig right now), but anyway, it's probably not the best tool for the job.
Anyway, sorry I don't have a better answer, but hope this can point you in some useful directions!