OpenFront.io Structures: 6 Core Buildings: Rules, Stats & Examples

All 6 Structures

Name	Cost / Formula	HP	Damage	Build	Upgrade	Role / Notes
Port	125,000 min(1,000,000, 2^n × 125,000), n = existing ports/factories	—	—	50t	✓ Upgradable	Naval hub: spawn base for trade ships, transports, and warships. Higher level = better trade ship spawn rate and revenue Can be captured; ownership transfers to the new occupier
Missile Silo	1,000,000 Fixed 1,000,000	—	—	100t	✓ Upgradable	Core infrastructure for launching nuclear weapons. Upgrades reduce reload time AI nukes avoid SAM-covered targets
Defense Post	50,000 min(250,000, (n+1) × 50,000)	—	—	50t	—	Land defense tower: significantly boosts defense within 30 tiles. Defense zone mag ×5, speed ×3 Destroyed rather than transferred when its tile is captured
SAM Launcher	1,500,000 min(3,000,000, (n+1) × 1,500,000)	—	—	300t	✓ Upgradable	Anti-air installation intercepting atom, hydrogen, and MIRV warhead nukes. Cooldown 90 ticks Range scales 70 → 150 tiles by level v33 treats in-flight MIRV warheads as normal SAM targets
City	125,000 min(1,000,000, 2^n × 125,000)	—	—	20t	✓ Upgradable	Raises population cap and participates in train trade. +250,000 troop cap per level Buildable even without a port (v24) Acts as a train station
Factory	125,000 min(1,000,000, 2^n × 125,000) (shares n with Port)	—	—	20t	✓ Upgradable	Spawns trains; combines with railways and cities to form a trade network. Train spawn rate (factories+10) × 15 ticks Builds railway loops

City — Population Factory

Each level +250,000 troop cap, max 4 levels = +1,000,000.
v24: no longer requires port first, can place anywhere (including inland).
Also serves as train station, defining railway network topology.

✦ City Build Order

Priority: 1st City > Port > 2nd City > DefensePost > 3rd City > Missile Silo. 4th city onward has diminishing returns—upgrade existing cities instead.

Port — Naval Hub

Enables trade ships, transport ships, warship spawning.
Higher level = better trade ship spawn rate and per-ship revenue.
Shares 2^n × 125k cost counter with Factory; build order determines which hits 6-figure costs first.

Factory — Train Production

Spawns trains and unlocks railways (max 120 tiles).
Train spawn rate: (numFactories + 10) × 15 ticks. More factories = denser train traffic.
Upgrades improve train throughput, but city count matters more for train economy.

DefensePost — Chokepoint Guardian

30 tiles range: mag ×5 / speed ×3.
Cost: min(250k, (n+1)×50k): posts 1-4 cost 50k → 100k → 150k → 200k, 5th+ capped at 250k.
Build time 50 ticks (5 seconds), can emergency-fill defensive gaps.

SAM Launcher — Nuclear Shield

Intercepts AtomBomb, HydrogenBomb, and in-flight MIRV warheads through the same trajectory and timing checks. The pre-split carrier is not a target.
Range: 150 − 480/(level+5): default 70 → level 5 ≈ 140, approaching cap of 150.
Build time 300 ticks (30 seconds), cooldown 90 ticks.
v24: AI nukes actively avoid SAM coverage, so first SAM provides deterrence value.

Missile Silo — Offensive Arsenal

Nuclear launch platform, build time 100 ticks.
Upgrades improve reload speed (shorter salvo intervals).
Multiple Silos required for simultaneous volleys.

⚠ Capture Rules Differ by Building

When territory is captured, SAM Launchers and Missile Silos transfer to the new owner, while Defense Posts are destroyed. Taking an enemy core can still strip its nuclear shield, but you must rebuild the land-defense layer yourself.