Ludii Update:
The state model for the hidden information has been completely rewritten in order to be much powerful and more generic. 
The previous system with visible, masked, invisible was not generic enough and is now removed. 
With the new model, this is now possible to modify for each player the visibility information for each data of a site (Count, Rotation, State, Value, What, Who) but also to make all the information completely invisible to a player.

Consequently, here the changes in terms of ludemes:
- In the starting rules, the hidden information are not set with the (place ...) ludeme but with the new ludeme (set Hidden ....).
- In the play rules, the hidden information are checked with (is Hidden ...), the sites with different hidden information for each player are gotten with (sites Hidden ...) and to set these information the effect moves (set Hidden ....) can be used.

For more information about these new ludemes, please read the Ludii Language Reference or the Ludii Game Logic Guide.