What kind of a game is Mother? Even now, it's difficult to give a real answer.
If some kids took some dolls out of a toy box, plates no longer used from the kitchen, found some nuts and bolts from a tool box, some leaves and flowers from the garden, lined them up on the carpet while singing a nonsense song, it would begin to describe that world. It's with that kind of feeling that Mother was made.
Well, I am an adult, so I'd add a few angles here, hide a few secrets there, and unabashedly add some really hard parts.
At that point, I'd have a bunch of friends come over to play, and with all their ways of having fun, I'd make them into the simple roots and base of a story, decorating it with twigs and leaves and flowers.