Just hit a milestone on some dev work, so a quick preview of what you can expect in the distant future. :
This video runs through some of the supported variants, and shows some of the UI updates required for their rules.
The board interface code has been rewritten from scratch along with the core legal move checking code (and plenty of other supporting code too.)
Variant support should be a lot less problematic in the future and will enable me to replace the guts of RHP with this updated code once it is thoroughly tested.
So,
960 (of course), Crazy House, Seirawan chess, Atomic, Antichess, Alice, Extinction, Cylinder, Horde, Three Check, King of the Hill, Racing Kings, Shatranj, Transcendental, Wildebeest , and whole lot more are actually complete.
As this is a massive change on top of all the other intended updates, this will take a long while before it is available to everyone / out of testing.
The current plan is to test this along with other prototype code on a new domain(site), and then roll the good stuff back in to RHP once everyone is happy. More on this later.
Edit : Video updated as one segment was missing.