Duo

Duo is a basic turret that fires alternating bullets from two barrels. It appears early in the tech tree as an inexpensive, item-consuming defense option and serves as a flexible starter turret capable of engaging both ground and air targets. Duo occupies a niche between the very early single-shot turrets and mid-tier rapid-fire batteries: it is cheap to build, can be fed by basic resource lines, and upgrades naturally into more advanced turrets once higher-tier materials become available.

Duo accepts multiple ammo types, each altering its performance. Copper rounds deal 9 damage and have an ammo multiplier of 2 items per shot; they are the easiest to supply directly from drills and furnaces but yield the lowest DPS. Graphite rounds deal 18 damage, have a 4 ammo/item multiplier, grant +2 tiles range, and impose -20% fire rate; their high per-shot damage is effective versus armored single targets but they are slower and costlier to produce. Silicon rounds deal 12 damage, have a 5 ammo/item multiplier, provide homing, and grant +50% fire rate; this ammo yields the highest DPS and tracks fast targets, but requires silicon production and power to sustain. Depending on version history, some past builds added or removed other ammo types and adjusted stats; current common behavior is that ammo types visually change the projectile colour when fired.

Duo’s baseline firing speed and range have been adjusted over multiple updates; it now fires around 3 shots per second with a range increased to approximately 20 tiles in modern builds, making it competitive with many early- to mid-game threats. Its barrels move separately while shooting, producing alternating shots rather than simultaneous volleys.

Practical usage and strategy:

• Use Duo as an early economical turret when only basic resources are available. It is most valuable where item throughput is limited and immediate coverage for both air and ground is required.
• Prefer copper ammo when supply simplicity is necessary; switch to graphite for handling tougher, armored enemies and to silicon when high DPS and homing are needed for fast movers.
• Duo is not ideal for anti-air specialization compared to dedicated anti-air turrets like the Scatter, because it lacks area damage and its base damage is modest.
• Against swarms, a Gamma or multiple light-effect turrets may handle enemies more cost-effectively than relying solely on Duos; groups of fast, high-damage units (e.g., Daggers, Novas, Flares) can take Duos down quickly due to their lack of piercing.
• Duo upgrades into more efficient turrets as higher-tier materials become available (for example transitioning into Salvo once titanium is reached) and is often replaced in well-developed bases by more specialized defenses.

Duo has cultural prominence within the game: it appears on the Mindustry app icon and serves informally as a mascot; an achievement also requires a Duo to deliver a killing blow on an Eclipse.