I don’t think reachable is permissible in the game, since reach-able means able to be reached, or possible to be reached.
Possibility is synonymous with to be able, so any term suffixed with -able should be forbidden.
The reachability explanation of possibility is also just one instance of possibility among many. to be able (without specifying in what manner) is the general type, and able to be reached is one particular (sub-) type of possibility. The more traditional understanding of possibility is able to exist, but others have been used too, such as able to be conceived, able to be done, able to be caused to exist, etc.
I don’t think reachable is permissible in the game, since reach-able means able to be reached, or possible to be reached.
Possibility is synonymous with to be able, so any term suffixed with -able should be forbidden.
The reachability explanation of possibility is also just one instance of possibility among many. to be able (without specifying in what manner) is the general type, and able to be reached is one particular (sub-) type of possibility. The more traditional understanding of possibility is able to exist, but others have been used too, such as able to be conceived, able to be done, able to be caused to exist, etc.