Since the last time I commented on this thread, I've learned quite a bit more about shields... I've also tried to make a complete categorization of frame advantage on shield. My conclusion? This is far from a trivial problem.
Firstly, there are 3 places you can hit a shield that produce 3 distinct results.
- Perfect shield
- Frame 1-3; allows for instant action. So, powershield to ZSS jab is likely the quickest shield response in the game with a minimum response time of 4 frames. (I forget if shield stun applies to power shielding).
- Shield, High Shield Lock
- There are 8 shield lock frames. You can't drop your shield, but you can jump or roll out of them. If you want an attack response and your foe is not in shield grab range, you'll have to wait this and your shield drop frames (7) to do so. So you'll have a minimum response time of 16 frames plus shield stun.
- Shield, Low Shield Lock
- If you have been in shield for at least 11 frames, your perfect shield window and your shield lock window are now gone, meaning any non grab, non jump cancelled response must only wait through shield drop frames. This yields a minimum response time of 8 frames plus shield stun.
This only gets more complex from here. Electric moves and moves with high hitstun multipliers cause your foe to lag a little more than you, producing some easier shield responses. Autocancel windows are all over the place... some moves benefit from landing immediately and eating the landing lag, and some moves benefit from waiting for the autocancel.
These are only response times. This doesn't account for spacing, shield push (which is negated near ledges), and the moves each character possesses as a retaliation. For instance, most characters can't really respond to... say... a spaced ZSS back air. Mii Brawler's 2nd up B can though (or was it the 3rd upB?)
So... ah... yeah. I'm still working on that complete categorization, and am attempting to make it automate updates for patches. We'll see how that goes.
