The core gameplay is that of a tower defense game, with a number of characters ("operators") as towers. Melee operators can be placed on ground tiles and ranged operators on elevated tiles. Melee operators physically block enemies from advancing, and ranged operators deal ranged damage, heal or otherwise support melee operators. Players must place operators on the correct tiles to prevent the enemy from infiltrating the player's base.
As the player progresses through the game, they unlock more stages, operators and resources, and are also introduced to new types of enemies and gameplay mechanics. Levels that have been cleared with a three-star rating can be auto-completed without player input, as the game records the player's actions and replicates them.
The game also has a base-building aspect, which allows players to construct facilities and assign operators to them. This allows players to increase their resources in the manner of an incremental game. It features the usual array of free-to-play, gacha game mechanics, such as daily login rewards and randomized character acquisition through virtual currency which can be obtained by playing the game, through limited-time events, or optional in-app purchases using real currency.