Knockback

Knockback is the distance a character flies when hit by an attack in the  series and Fraymakers. It is measured in pps, or pixels per second. For instance, 's fully charged forward smash in Super Smash Flash 2 does 9 pps of forward knockback to an opponent at 0% damage. A player can avoid receiving knockback when under the effects of invincibility, intangibility, or knockback resistance.

Certain attacks have special properties in terms of knockback. Set knockback, sometimes referred to as fixed knockback, is a property of some attacks in Super Smash Flash 2 and Fraymakers in which the knockback dealt by the attack is static in that it does not depend on the opponent's percentage. Some of these attacks deal set knockback based on a character's weight, called weight knockback. Additionally, several attacks deal zero knockback despite dealing damage.

Conditions
This is a list of conditions the knockback of an attack depends on:
 * The current damage of the opponent.
 * The current movement speed of the opponent.
 * The damage dealt by the attack.

If the damage dealt on a character's attack matches the damage given by their, that attack will deal vertical knockback. Every character's up attack deals the same damage as their down aerial. Other attacks will inflict horizontal knockback.

Attacks with horizontal knockback will send opponents three knockback units forwards and one unit upwards (about 18.435°), while attacks with vertical knockback will send opponents one knockback unit downwards (if said attack is a down aerial) or upwards (if said attack is not a down aerial). Attacks with vertical knockback will take the opponent's current movement speed into consideration when calculating the total knockback, sometimes resulting in an instant-KO.

Conditions
This is a list of conditions the knockback of an attack depends on:
 * The current damage of the opponent.
 * The weight of the opponent.
 * The damage, base knockback, and knockback scaling of the move used.
 * Whether the opponent is charging a smash attack.
 * The launch rate of the match.
 * The damage ratio of the match, which is normally 1 outside of certain Solo modes.

Knockback values
Each hitbox of a move has two knockback values: a base knockback and a knockback scaling (also known as knockback growth).

Base knockback, referred to as power in the code, is the minimum amount of knockback that an attack can deliver (in normal circumstances), and knockback scaling is a factor that controls how much knockback increases as damage increases. Moves with high base knockback deal high knockback under any circumstances, such as the swing of the Home-Run Bat. They additionally tend to be more effective at KOing when less knockback is needed (ex. light characters who are near the ledge or when an opponent is handicapped to sustain more knockback).

On the other hand, moves with high knockback scaling take less damage to reach KO potential, such as 's forward smash. They additionally tend to be more effective at KOing when the opponent requires more knockback to be KO'd (such as against heavier characters, when far away from a stage's blast line, or when an opponent is handicapped to sustain less knockback). Techniques such as Directional influence and Momentum canceling who help extend a players survival becomes less effective the stronger an attack's knockback scaling is.

List of set knockback attacks

 * Many neutral attacks.
 * 's neutral aerial and forward aerial (weak hits).
 * 's down smash, and.
 * 's up smash (first hit).
 * 's forward smash (weak hits), and up smash (first hit).
 * 's up aerial (first hit) and.
 * 's.
 * 's down smash (weak hits).
 * 's down aerial and Vine.
 * 's dash attack (weak hits), down aerial, and Inhale.
 * 's down aerial (weak hits).
 * 's up throw, (weak hit), dash attack (weak hits),and.
 * 's down aerial,, and Cape.
 * 's Shadow Clone Slash.
 * 's up throw.
 * 's neutral aerial.
 * 's forward aerial (weak hits), and Quick Attack.
 * 's floor attack.
 * ' forward aerial and up aerial (weak hits), and forward smash (first hit).
 * 's up smash (first hit).
 * 's up smash and down smash (weak hits).
 * 's up aerial (first hit), and.
 * 's down smash, and Chomp.
 * 's up smash (weak hits).

List of no knockback attacks

 * 's.
 * 's Mega Buster (level 1, late hit).

Formula
The knockback formula used in Super Smash Flash 2 is similar to the formulas used in the  series. For attacks with no set knockback, the following formula is used:

${[((p ~ + ~ d) ~ \times ~ 0.1 ~ + ~ d ~ \times ~ (p ~ + ~ d)) ~ \times ~ m ~ \times ~ 1.4 ~ \times ~ \frac{200}{w ~ + ~ 100} ~ + ~ 18] ~ \times ~ k ~ \times ~ 0.01 ~ + ~ b}$, where $p$ is the current damage percentage of the opponent, $d$  is the damage the attack deals, $m$  is a multiplier set to 1 by default, $w$  is the weight of the opponent, $k$  is the attack's knockback scaling, and $b$  is the attack's base knockback.

For attacks with set knockback, the following formula is used:

${[(s ~ \times ~ 10 ~ \times ~ 0.05 ~ + ~ 1) ~ \times ~ m ~ \times ~ 1.4 ~ \times ~ \frac{200}{w ~ + ~ 100} ~ + ~ 18] ~ \times ~ k ~ \times ~ 0.01 ~ + ~ b}$, where $s$ is the set knockback.

For both formulas, the total knockback is then multiplied by 1.2 if the opponent is charging an attack, and it is finally multiplied by both the launch rate and damage ratio of the match.