Thanks, but I don't even know what "HSD" is (my guess is "Hit Stun Deterioration"?). I try searching on YouTube and it's a bunch of videos of how to do "it" with a particular team or setup, but not an explanation of what I'm looking at.
I suppose I'll take another look and try to decipher it myself. From what I can tell, it's basically a universal infinite achieved by repeating button sequences when certain conditions are met.
You are correct that HSD means hit stun deterioration. One mechanic baked into the engine of many fighting games, including MvC:i is that the longer a combo goes, the shorter the hit stun a move can put you in. This is to prevent infinites, as once the hit stun deteriorates far enough, the combo cannot possibly continue because with so little hit stun, it's impossible to combo moves together any longer.
In Marvel 3, hit stun deterioration was timer-based, i.e., there was an internal clock that started ticking when a combo began and the longer it went, the shorter hit stun became until it bottomed out and moves did whatever their minimum hit stun value was (of course, there were still very long combos in marvel 3 because many moves still combo'd even at their minimum hit stun values, allowing things like Vergil's spiral sword loops). Apparently in MvC:I, the way it works is that hit stun deteriorates based on the amount of damage in the combo thus far. It seems like once a combo gets to around five or six thousand damage, it's nearly impossible to keep the combo going with exception of tacking on supers to the end. This is why most players think that optimizing combos past a certain point is almost irrelevant, as the hit stun deterioration means any decent combo is going to end up doing the same damage.
The glitch is if certain conditions are met, hit stun deterioration is set back to some lower value and is frozen there, allowing much longer combos and even infinites. If the tweet I linked is correct, the conditions for triggering the glitch are you must cross the 7,300 damage threshold while performing an OTG into a super. As long as after that you keep the opposing character in hit stun, the hit stun deterioration is frozen.
