All character skills underwent considerable changes during development, with perhaps the biggest change coming before [[BlizzCon 2010]] -- skill trees were removed (but the tiers remained), and passive skills were separated out from the skill listing and renamed [[Traits]]. The second big change occurred when skill tiers were removed for the [[July 2011 Press Event]], allowing skills to unlock steadily from levels 1 to 30; also, traits were renamed back to passives. Finally, the [[Beta Patch 13]] introduced a new categorization system, which placed each skill into one of 6 (fairly arbitrary) new categories for each class.<noinclude>