Control Failure

Will someone PLEASE tell me why the action button isn’t working? This is getting extremely frustrating. I’ve tried to go into the settings.txt file and modify the controls but I get a “you do not have permission to modify this file” dialogue every time. I’ve even tried going into “get info” and changing the read-write permissions.

I find it incredible that I payed ten dollars for a game that I can’t even play. SOMEONE PLEASE HELP

cully g about LIMBO by Playdead