I always read something like HTML5 games etc. But I don’t believe that a game is entirely programmed in HTML5 because it is just a markup language. Normally, it is controlled though JavaScript, right?
I want to program a very very simple browser game, that I can play with my friends. But I want to code the logic in Scala.
So I came up with this structure.

The client is able to see HTML in his browser. HTML5 will be manipulated though JavaScript which opens a connection to my webserver (AJAX?). Now I can program all my logic in Scala and let JavaScript execute it (for example move pawn from position a to position b).
This would be possible, right?
As a webserver I would choose Lift.
But I have never done any rendering with JS/HTML5. Would you recommend to look in some frameworks such as LimeJs or CraftyJs?
“HTML5” is commonly used as an all-encompassing reference to a set of specifications for client-side scripting language APIs, in addition to the core markup language that gave rise to the “ML” part in the name. So “implement this-or-that in HTML5” generally means something like do it in client-side Javascript, manipulating a DOM tree as specificied by HTML5 in order to present a user interface.
It is somewhat inconsistent/illogical naming, but standardizing on inconsistent illogical terminology is what this industry is best at. 🙂