Yep, definitly the easiest strategy.
Lower left slot: Spread machine gun.
Top left slot: Damage buffer.
Rest: Barriers.
With this setup nobody should have problems to get the hard badge.
Hey everyone. I have a problem with this game. I finished the level 77 with the 5th Guardian, but the last level does not appear on the map. I didn't play every level, but I don't think that this matters, or am I wrong?