Couple of questions

Will try here but this forum seems surprisingly dead.
Regarding pits, the deeper i go the more times i get a fight and everything seems to stop and half the screen goes dark, is this intended or a bug?
In boss fights around depth 140 i bang away at the boss and hardly move his health bar until BOOM 1/2 or more of the bar just disappears, is this the magical trillion hit? and if so how can i make it happen more lol.
Thanks.