Claudus
An orange-cored machine with a shield, a flood of code, and bots that make it untouchable while they live. It is the third of the nine bosses.
I've thought about it carefully. You lose.
The stages
Claudus is fought in stages. First come bots you mostly have to dodge, then drones that arrive together with a shield around the boss, and finally the code phase, which stays for the rest of the fight.
The code phase
In the code phase streaks of falling code rain down the screen, leaving a safe corridor that slowly wanders. Waves of code bots arrive as well, in three waves of growing strength.
While any bot is alive the boss cannot be hurt, and your shots are simply used up on it. After you clear a wave there is a short opening to damage Claudus before the next wave comes in.
Other attacks
Claudus also uses diving orbs, and it reflects orbs back at you when your shots land on it: as a single orb, a fan of three, or a quick snapping one.
Tips
Clear the bots quickly and spend the openings on the boss rather than on stray shots. Watch the corridor in the code rain, since it is where the safe space is.