Destroy the Left
Trackers (weak against Repeater) will bounce off of the HR-D if they come in contact with him. Destroy them and keep them out of the right. Guards (weak against ScatterShot) stay put for the most part. They don't cause much trouble other than blocking your path and taking your upgrades. If you shoot them with the wrong weapon you will lose points so pay attention. Voids (weak against Missiles) will spawn towards the top of the screen. They are the most valuable enemy.
Bonuses are listed, and highlighted when enabled, at the bottom of the screen. They are primarily Recovery, Kite, Rushin' Firewall, and Low Health. You will activate these by the actions that transpire on the Right side.