saves by default go into XDG_DATA_HOME/sm64pc
external data is read from the executable directory, if it's not found there on Unix systems the game will attempt to read it from some paths like /usr/local/share/sm64pc
both save data and readonly data fall back to other options in case of a problem
behavior can be overridden by specifying --datapath and --savepath on the CLI
both of those will expand the exclamation point ('!') to the executable path, e. g. --savepath '!/save'
