Structures

Structures are buildings which you can place almost anywhere. Like the NPCs, the structures are found the bag icon and needed to be bought with the money ingame. The structures need five seconds to deploy. The structures could be walls or defensive units.

Upgrade guide
Each structure has five upgrades. However, while the players and NPCs need money, structures need technologies. You can get technologies by passing missions, destroying MOAB-class bloons, some bloons or if you buy some with money.