From Galaxy Attack: Alien Shooter Wiki
Upon Evolve activation, if you have Defence Matrix selected on your ship, you have a chance to summon a turret that shoots down incoming projectiles.
In practice, this appears like a large shield around your ship, protecting it from bombs and fireballs.
The chance of Defence Matrix triggering on Evolve activation is as follows:
Clearly, you need to have Evolve enabled on your ship, otherwise this Expert Item will have no effect.
Tip: Don't put this Expert Item on Pirate or Tyrant, because these ships already get a shield when Evolve starts, and so you won't benefit from the matrix.
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