I get a whole bunch of PMs from people checking out the Help room asking why the format they built their team for is not available to play via the "Battle!" button on the homepage. To those players new to Showdown, this gets insanely confusing. So I figured it'd be a great idea to visualize this in the teambuilder format selection. Perhaps bolding the formats available on the ladder, or even turning those green. Or adding a sub-category for "ladderable" and "non-ladderable".
