Talk:Mirrorsnatch!/@comment-86.142.116.27-20130405111544/@comment-4085424-20130405140319

There's a section in the Reference Guide specifically on this. The winner gets some change to a quality, the loser gets the opposite change - but only if neither goes below zero. So in this case trying to steal from someone with zero Mirrorcatch Boxes can't take them to -1, therefore doesn't get to increase to +1. It's fiddly but obviously helpful for cases like this.