Arknights is a free-to-play mobile game developed by Hypergryph and Bilibili. Outside of China, Arknights is published by Yostar and Longcheng. Arknights is unique in which it mixes elements from both tactical RPG and tower defense games, which contributes to its rising popularity both in mainland China and worldwide following the game's international release. While the game features gacha game mechanics, Arknights is generally seen as among such games who are less "predatory" than others. The game is exclusively played in single-player mode, although a cooperative system between players is featured.