Researches are organised in linear pathes with no pre-requisites between branches. Once a research is done, the next ones become available.
The deeper a research is in a branch, the more it costs to research.
Each weapon class has it's own research path, which starts with the tier 1 turret. Once the tier 1 is available, the next tier becomes researchable as well at the upgrade branche. Each class has 3 upgrades that roughly increase effectiveness by 15-20% by augmenting damage and rate of fire.
Researching a weapon will unlock the basic defense structure, tower or emplacement according to the weapon type. To unlock bunkers, hardcrete wall is required. Artillery are not available in bunkers.
The sensor path starts with the regular radar.
A radar turret has a long line of sight. Artillery units can be assigned to a sensor to share it's attack order and automatically target units that are detected by the radar. Non assigned units will automatically attack only within their line of sight but can still be manually asked to fire further as long as an ally has the target in sight.
Artillery emplacements must be built near a sensor turret to be able to fire at full range, as they cannot be ordered manually.
VTOL strike turrets are similar to regular sensors but will order the assigned VTOLs. Counter-battery turret will target enemy artillery that target within the sensor range. Even if the artillery unit is out of sight, a counter-attack is ordered.
Wide spectrum sensor combines all of the above turrets. Radar detector acts like a standard radar but with long range.
At the end of the path, the uplink centre will reveal all the map while the building is running and the laser satellite command can order a satellite strike anywhere on the map once in a while. Even if you see any units with the uplink centre, an ally unit must still have a direct sight of the target for artillery to target it.
The repair path is composed of the light and heavy repair turrets, and finally the auto-repair ability.
The vehicle body path starts with medium bodies and Nexus small body. Once the medium body is researched, large body becomes researchable. To be able to research medium and large Nexus bodies, the regular ones are required.
Armour upgrades can be researched once medium bodies are available. Each of the three upgrades provide +10% HP to your units.
The structure path starts with the hardcrete wall, which will unlock bunkers once the weapon is researched (the bunker itself must still be researched at low cost due to some engine limitation). Next are the 3 building upgrades which increase the hp of buildings and defenses.