Hitstun

Hitstun, referred to as hitlag in the code, is the period of time where after being hit by an attack, characters cannot do anything, but DI and/or tech if they come into contact with a platform, wall, or ceiling. It scales with damage, although starting values can vary. It begins right after hitlag ends.

Hitstun is an essential component of combos, as the basis of a combo is to have enemies not being able to interrupt or prevent the player's combo from happening.

In Super Smash Flash, each character has a stat with a set that dictates how long their hitstun lasts, whereas in SSF2, hitstun's duration is a stat placed on the attack itself, and it scales according to the knockback dealt to the opponent.

In Super Smash Flash 2, unlike in the official games, hitstun is not cancellable (when excluding teching). When a meteor smash hits a grounded foe, hitstun is multiplied by 1.2.

Flinching
In SSF2, characters flinch during hitstun caused by an attack that deals low knockback. This frequently happens when characters are at a low percent. Characters will also always flinch during hitlag. In SSF, characters will flinch for a set time regardless of knockback amount. In both games, characters will revert to their falling animation once the knockback diminishes and this animation ends.

Reeling
Reeling is an animation that plays during hitstun in SSF2; characters enter a helix motion. Characters will enter this state after being hit by an attack that deals high knockback or a few attacks at high percentages. Once the knockback diminishes and the character slows down, both reeling and hitstun end, and tumbling begins. Reeling happens commonly and with every character, but not every character currently has a proper animation for it.