Duo

Duo is a small, inexpensive dual-barrel turret commonly encountered in the campaign and used for early-game base defense. It fires alternating bullets from two barrels and accepts multiple ammunition types (Copper, Graphite, Silicon) that change its behavior. Duo’s effective range and firing visuals were expanded in later versions so its shots now show ammo-specific colors; the turret’s range reaches 20 tiles in current builds.

Duo is a versatile starter turret but is generally intended for the early stages of a match because more advanced turrets outclass it once higher-tier materials are available. It can target both ground and air units, but it lacks piercing or area damage by default, which limits its effectiveness against swarms of lightly armored, fast units or heavily armored single targets without using the appropriate ammo.

Ammo behavior and practical effects:

• Copper: 9 damage, 2 ammo per item, resulting in 27 DPS at base fire rate. Copper is easiest to supply directly from drills but has the lowest damage and is recommended only for the earliest defense.
• Graphite: 18 damage, 4 ammo per item, grants +2 tiles range but applies -20% fire rate, yielding about 43.2 DPS. High single-shot damage makes Graphite effective against armored units, though it is slower and more resource-intensive to produce than Copper.
• Silicon: 12 damage, 5 ammo per item, +50% fire rate, and adds homing to bullets, producing 54 DPS and strong performance against fast targets. Silicon provides the highest DPS and homing capability but competes with other silicon uses (units, advanced production) and requires more infrastructure.

Booster interactions and supply notes:

• Duo can be boosted to increase its fire rate. Boosters consume at 6 units/sec and modify fire rate; common booster levels provide 140% or 190% fire rate depending on the booster fluid used.
• A new item deposit cooldown of 2 seconds applies when loading ammo, making rapid manual reloading less efficient.
• Barrels now animate independently when firing, and ammo colors are shown on projectiles to indicate which ammo is in use.

Tactics and deployment:

• Use Duo as an early, cheap defensive option or as filler when materials for superior turrets aren’t available. It is frequently one of the first turrets players unlock in campaign play.
• Prefer Graphite when facing armored single targets; prefer Silicon when you need homing and the highest DPS against mobile enemies, and use Copper only for the most resource-constrained situations.
• Duo is not recommended as an anti-air specialist since it lacks area damage and piercing; use dedicated anti-air turrets like the Scatter for that role.
• Grouping multiple Duos can cover both ground and air approaches, but clusters are vulnerable to units with high damage-per-shot (Daggers, Novas, Flares) that can eliminate turrets quickly.
• Once titanium becomes available, consider transitioning from Duo to more efficient turrets such as Salvo for sustained high performance.

Trivia and legacy:

• Duo appears on the Mindustry app icon and is often treated as an informal mascot for the game; it is jokingly called the “ultimate turret.” The Steam achievement “Against All Odds” requires a Duo to score the killing blow on an Eclipse.