As the Narsians begin their charge, the Kepler Mecha launch a furious salvo back at them. Blue Kepler Plasma and White Ion charges meet Purple Narsian Plasma shots in midair, causing spectacular explosions, while the rounds that barely miss each other cause the surrounding atmosphere to crackle with localized lightning as the opposing charges attempt to equalize in the fraction of a second where they are in close range to each other.
Most of the mecha are only doing the most basic job of aiming, treating the mass of attackers like a solid wall that they simply need to put rounds into and break down before it reaches them.
It might not be elegant, or even particularly efficient, but at first, it is doing the job well enough. The volume of fire is thinning the enemy ranks much faster than the return fire is thinning their own.