I've been working for some time on a capture the flag web game called Rock Paper Scissor Battle!, which is basically a simplified version of Stratego, but the pieces are rock, paper and scissor instead of numbers). Its open source on my Github: https://github.com/daniel-bytes/rps-scala, the backend is Scala and Redis and the frontend React + Typescript. I have a live version of it up at http://rock-paper-scissor-battle.com/, although I have a feeling any real level of traffic will topple over my $5/mo Heroku dyno. Also don't mind the goofy font landing page. :)

I'm overall happy with the backend code, except for the "AI", which can use some real work and research. Right now just some basic semi-random rules that make it pretty easy to beat.