User:JeffreyLau/SC2/Frame advantage and fundamental strategy

Frame advantage
All animations in SC2 are discretized into frames. The SC2 engine runs at 60 frames per second. Thus, a 12-frame attack (for example) takes 0.2 seconds to execute. Such an attack is called i12, short for "impact 12," meaning that the attack hits the enemy 12 frames after it is executed.

Intro
When an attack hits or is blocked, both players enter a recovery animation in which they recover their stance and cannot move or perform any actions. Depending on the attack, and depending on whether it hit or was blocked, one of the two players will recover faster than the other. This is referred to as frame advantage. Over the course of a fight, the two players will shift in frame advantage many times.

Example
Frame advantage is best illustrated with an example:

Ivy succesfully hits Mitsurugi with her 2A. Ivy's 2A gives +7 frame advantage on hit. This means that Mitsurugi's next action-- block, attack, GI, or move-- is delayed by 7 frames.

Suppose Mitsurugi tries to attack with A. Mitsurugi's A is i10, meaning it takes 10 frames to execute. But since Mitsurugi is suffering a 7-frame disadvantage, the attack actually comes out in 10 + 7 = 17 frames. This means that Ivy can do any attack that is i16 or slower, and she will beat Mitsurugi. For example, she may try 66B (which is i16), and score a counterhit against Mitsurugi, leading into a high-damage combo (CH 66B, 6B9). If Ivy attempts a move that is i17, she will probably clash or trade hits with Mitsurugi. If she does anything i18 or slower, Mitsurugi will beat her with a CH.

Note that Mitsurugi can still block any of Ivy's attacks, since none of Ivy's attacks are faster than i7 (her fastest moves are i11).

The mixup
Now we get to the most important element of SC2 strategy: the mixup. What do you do if you have a large frame advantage over your opponent? Since your opponent has too much disadvantage to counterattack, he is forced to block or GI your next move. This is where you can make him guess: should he block standing or crouching?

Your basic mixup is between:
 * Lows and throws, if he stands
 * Powerful mids, if he crouches

Oftentimes, these two options won't be balanced in terms of reward (mids usually do more damage). So he's more likely to block standing than crouching. But, if you know this, you can get free damage by always using lows and throws. But if he knows you know he always stands, he'll start crouching more often. But you can top him again by mixing your mids back into the game. And so on...

"But wait," you say, "4G (GI) defeats both mids and lows!" This is true... sort of. First, 4G will not defeat throws. Throws must be GI'd with 6G. Second, GI'ing will only defeat the mid/low mixup if the mid and low are approximately the same speed. If one of them is slower than the other, his timing will be off (but of course, slow attacks are easier to block on reaction). Third, if you know your opponent will GI, you can simply wait for him to GI and then attack while he's vulnerable, or use a slow move with a deceptive windup to bait him into GI'ing. Nevertheless, GI'ing is a good way to punish opponents who use predictable mixups.

Implications
The fastest moves in the game are i10. Thus, a move is considered safe if it is -10 or better (more positive) on block. This means that, even if the opponent blocks the move, he doesn't get any free damage. If a move is -11 or worse (more negative) on block, the move is unsafe. Your opponent could theoretically punish you with an i10 move and there is no way to defend-- you can't block, move or GI in time to stop him. Of course, there are varying degrees of safe and unsafe.

Knowing what moves have what frame advantage on hit and block is a big part of high-level SC2. Don't be daunted, though; you don't need to memorize this data at first (even pros don't need to memorize every move's frame data), though you should eventually learn the frame data for at least a few of your character's key moves.

General trends
For now, just remember these general trends about frame data:


 * Most moves give + frames on hit and - frames on block.
 * Low moves typically have worse frame data (less + on hit, more - on block), since they're harder to defend against.
 * Basic pokes-- A, B, K, 2A, 2B-- are usually fast, safe, and give good advantage on hit. This is balanced by their low damage.
 * Fast moves that lead to high damage are typically unsafe (they can be punished if you block them).
 * Some moves can be charged up, e.g. Ivy's ass kick 1[K]. Charged moves are usually safer than uncharged, and many of them even give + frames on block.
 * Moves that give + frames on block are very valuable since they allow you to keep up your pressure against your opponent. But there are very few of them.

Fundamental strategy
Fundamentally, your SC2 strategy should revolve around doing one of two things for most of the match:


 * 1) Gaining frame advantage
 * 2) Converting frame advantage to damage, with mixups

And that's it.

If you're at a frame disadvantage, you should try to neutralize your opponent's attack flow, to get the advantage back. If you're at advantage, you should work on increasing that advantage (if it's small), performing mixups (if it's large), or cashing it in with guaranteed damage (if it's really large, like you've just popped your opponent into the air).

This is why most games tend to feature back-and-forth blocking and attacking phases. One player pushes the attack until the other one blocks. By blocking, the defender gains a frame advantage, and now he is free to start his own attack. Real matches tend to be more staccato than this, since people take risks, try to interrupt each other, etc.; but this is basically how it goes.

Ring-outs (ROs)
Sometimes it's advantageous to play for a ringout (RO). Not every character can RO in every direction. Some (e.g. Astaroth) are much better at RO than others (e.g. Taki). The most useful thing about RO, though, is that you can easily corral your opponent into doing what you want, since the penalty for ignoring you is instant death. For example, if you have a high backwards RO like Ivy's A throw, you can bet your opponent will duck whenever you back is to the ring. You can use this to your advantage by hitting him with power mids. (Ivy happens to have a mid backwards RO too-- FC 1B-- which is really nasty since your opponent can't defend against both attacks!).

The threat of a RO also makes people try to escape from the ring edge, so you can use more horizontals and catch their sidesteps.

Ground attack (okizeme)
Ground attack, or okizeme in Japanese, means trying to hit your opponent after you've sucessfully knocked him down. You can often force a mixup on the ground, by making your opponent guess whether he should roll right or left, or stand up or crouch. Okizeme plays a lesser or greater role depending on your character (for example, Mitsurugi's oki game is much stronger than Ivy's). No matter what character you play, though, you'll frequently have opportunities to go for okizeme, so you should be familiar with your character's good ground-hitting moves.

Okizeme strategy is character-specific so I'll talk about it more in the Ivy section.