Many of you know dynamic geometry exercises in Euclidea; if not, here is one example. It lets you do a geometric construction and sends a message once you achieve the result.

I am looking for a way to produce exercises for students in a similar form. At the moment I use C.a.R. which uses Java plugins. But as you may know, all major browsers stopped supporting Java plugins in 2014 or so. So I have to make my students install JDK (or OpenJDK) which is not fun.

There is plenty of software that does dynamic geometry, but as far as I see nothing else has the exercise mode that I need; or did I miss something?