Essentially a hero-based shooter, Overwatch assigns players into two teams of six, with each player selecting one of 24 pre-defined hero characters with unique movement, attributes, and abilities whose roles are divided into four categories: Offense, Defense, Tank and Support. Players on a team work together to secure and defend control points on a map and/or escort a payload across the map in a limited amount of time. Players gain cosmetic rewards that do not affect gameplay, such as character skins and victory poses, as they continue to play in matches. The game was initially launched with casual play, with a competitive ranked mode, various 'arcade' game modes, and a player-customizable server browser subsequently included following its release. Additionally, Blizzard has developed and added new characters, maps, and game modes post-release, while stating that all Overwatch updates will remain free, with the only additional cost to players being microtransactions to earn additional cosmetic rewards.