This does not need to be an observable as it is used only internally and 
in 1 component, which needs the new state only after calling update 
functions. Those functions can return the new value directly instead of 
via observable. And for store internal use a simple variable is 
sufficient.

Now there is a button at the side that can be used to slide the panels 
in and out.

There it can be used by the player as well.