Hey, Bryan. Thanks for the suggestion. I've thought about doing this, but there are a few reasons why I haven't yet: 1) It's kind of hard (ok, not a great excuse). 2) The site would be twice as slow because it would have to run twice as many queries, and already, things are not as fast as I would like. 3) The logic doesn't always make sense. For example, if I have two players on and 1 off, do I want to switch it around and have 1 player on and 2 off? 

The way I've been thinking about implementing this is allowing the user to setup a "chain" of queries, and then running them and returning the results. It wouldn't be the default behavior, and it would be a little bit more complicated from a UI perspective, but it would essentially give you what you want: a way to calculate +/- without having to run two separate queries and flipping back and forth. I'm hoping I can get around to implementing this in the near future, but it's not a trivial thing from a UI perspective or from the backend.