Hearthstone, originally known as Hearthstone: Heroes of Warcraft, is a free-to-play online collectible card video game developed and published by Blizzard Entertainment. Having been released worldwide on March 11, 2014, Hearthstone builds upon the already existing lore of the Warcraft series by using the same elements, characters, and relics. It was first released for Microsoft Windows and OS X, with support for iOS and Android devices being added later. The game features cross-platform play, allowing players on any device to compete with each other, restricted only by geographical region account limits.
The game is a turn-based card game between two opponents, using constructed decks of thirty cards along with a selected hero with a unique power. Players use mana points to cast spells or summon minions to attack the opponent, with the goal to reduce the opponent's health to zero. Winning matches can earn in-game gold, rewards in the form of new cards, and other in-game prizes. Players can then buy packs of new cards through gold or microtransactions to customize and improve their decks. The game features several modes of play, including casual and ranked matches, as well as daily quests and weekly challenges to help earn more gold and cards. New content for the game involves the addition of new card sets and gameplay, taking the form of either expansion packs or single-player adventures that reward the player with collectible cards upon completion.