This is really interesting, never saw that before. I've long been thinking of starting a hobby project for a general purpose board gaming rules engine. Guess it's already there!

If you are more interested in the rules/logic side of things there’s also https://boardgame.io/

As a person who has used VASSAL, there is a lot of possible improvements that could be made.

TTS is pretty solid IMHO. I rather like it. But this is interesting to me. Thank you. Have you used it to playtest a novel game?

I've made a couple of Vassal modules over the years, but of existing games, but yes, I could see it being useful for playtesting.

Wow, I had never heard of it, thank you so much for the link!

is there a android version? Because some years ago I played it with jobmates and it was great.