Building upgrade needs resources. Only ores are needed in the early stage while steel is needed in the middle and late stage besides ores.
Headquarters: Upgrade can unlock more buildings and increase resource storage capacity.
Barracks: Upgrade can unlock Units.
Fuel Depot: Upgrade can increase resource storage capacity and decrease the loss when plundered.
Resources Vault: Upgrade can increase resource output and storage capacity.
Research Center: Upgrade can unlock technology and increase technology cap level.
Tactics Center: Upgrade can unlock tactics and increase tactics cap level.
Training Center: Upgrade can increase Units’ cap level.
Mining Factory has resource storage capacity, and it stops producing after reaching max resource storage capacity.
When the resources you obtain exceed storage capacity, you can upgrade Resources Vault and Headquarters to increase resource storage capacity.
Headquarters: Upgrade can unlock more buildings and increase resource storage capacity.
Barracks: Upgrade can unlock Units.
Fuel Depot: Upgrade can increase resource storage capacity and decrease the loss when plundered.
Resources Vault: Upgrade can increase resource output and storage capacity.
Research Center: Upgrade can unlock technology and increase technology cap level.
Tactics Center: Upgrade can unlock tactics and increase tactics cap level.
Training Center: Upgrade can increase Units’ cap level.
Mining Factory has resource storage capacity, and it stops producing after reaching max resource storage capacity.
When the resources you obtain exceed storage capacity, you can upgrade Resources Vault and Headquarters to increase resource storage capacity.