I was just playing a game, and Black Heart MkII moved offscreen in such a way, that he never came back, and the next boss sequence was triggered ;-P
I'm wondering if this is just an emulator related bug, or if it's part of the actual game.
Exactly what happened was; I milked his first phase for a little bit with those grenades he tends to fire, then he changed firing mode to where he moves erratically (but still in the first phase). The erratic movement firing pattern ceased in such a way that he was about halfway down the screen (maybe further), and he resumed his horizontal sweeping patterns at this new location.
Phase 2 is triggered by a time limit or damage threshold, after which he cuts his engines and drops vertically down the screen by a static amount. If Phase 2 starts when he is at the top of the screen, then he'll merely come close to you and then return to the top. Though sometimes, if his erratic pattern has left him lower down the screen, he can indeed squish your ship.
So when I triggered Phase 2 with him so abnormally low on the screen, I knew I'd be squished so I just sidestepped and let him do his maneuver. I expected him to go below and offscreen, which he did, but I figured he'd come back. But no, the second he went offscreen, the pre-Glow-Squid divebomb ships appeared, then Glow Squid itself... and never again did I see Black Heart D-:
Anyone know how to control his motion? >:-)
"Random" enemy movement/positioning seem to be based on player position, so I assume BH MkII follows the same rules...