Headdy baby face notes

Baby Face discoveries:

All phases won't start moving until you hit them for the first time. The shell of the previous form has to be mostly off-screen for the shot to count, then they'll move after the shell is fully off-screen. The frame you shoot them in between "first frame the shot counts" and "first frame they're allowed to start moving" doesn't matter; it's a half-second window, because what it is is that, once the phase change is complete, they'll start moving if they're currently invulnerable (i.e. don't get yourself hit by the shell! take your time)

If you care, don't spam shooting them once a phase is over and you're waiting for the shell to come off, as it seems to delay the shell coming off by a few frames. So, hold B until phase is over (projectiles explode), don't shoot while shell is coming off, spam shoot once you've moved around the shell to get them to start moving

Baby Face will move towards your position, but your distance doesn't matter (your position just sets his angle; then he moves a set distance towards you, and then a set distance back to the center)
Then, once he reaches the center, he'll go towards you again
This means that you can manipulate a faster two-cycle. For consistency, I've been hugging the left wall for it.
For example, I've been having luck by having him go pretty high for the first phase (Headdy lined up with the line in the background), and then pretty low for the second phase (Headdy lined up with the line above Don't Fly signs, or a little lower), and I'm able to avoid balls in between (although I tank a hit if need be once he's about to be in the center)
Being centered/too high both times makes a slow safe two-cycle; too low could result in an awful three-cycle.

Boy Face doesn't start taking damage until he reaches the right side of the screen and stops moving! If you just spam shots at him, the invuln timer will make a two-cycle Boy Face far harder than if you time your first shot against him to be at this time.

Man Face has the same health system (takes no damage until he reaches the right side), although his one cycle is long enough that 2-cycle is never really a risk if you stay aimed on him.

Baby Face's health RAM address is D235, and invuln timer is D237
Each phase starts at 128 health, and will go down to 96, then needs one more hit, for 33 hits per phase
I recommend watching the health address to check out Boy Face's first hit timing, and play around with Baby Face positions and see how long it takes for him to end once he's at 96-1 health