The Developer is a defense game where the protagonist, a developer, successfully activates a control device to defend the planet from alien lifeforms and secure planetary domination.
Turrets pre-installed by the vanguard are scattered across the map and are used to fend off alien waves.
Each wave consists of a unique combination of monsters including melee, tank, ranged, and assassin types. A boss monster appears in the final wave.
When all monsters in a wave are eliminated, the wave ends.

Turrets include Cannon and Missile types, each with 3 levels. The number of bullets or missiles they can fire increases by level.
Since turrets operate within the total power capacity of the control device, the player must manage turning them on and off strategically.
The player also has a weapon, allowing them to lure enemies and defend blind spots of the turrets.
If either the player or the control device runs out of health, the mission fails and the game is over.
If the player successfully survives all waves, the mission is considered a success and they move on to the next planet.

The game is story-driven, allowing players to immerse themselves more deeply by following the storyline.