Interruptibility
Interruptible as soon as frames, abbreviated "IASA frames," are a set of frames that occur during the final period of certain attacks and other actions, during which a character may immediately launch into a new attack or action without having to wait for the cool down animation to finish. Hence, the attack or action is "interruptible (with a new action) as soon as" this set of frames begins. IASA frames occur in all three Super Smash Bros games.
Of particular note is Pichu's right facing taunt, the animation for which lasts 100 frames, but can be interrupted with another action after only 60 frames. Hence, the taunt has 40 IASA frames. In the case of attacks, IASA frames usually occur after hitboxes disappear, but before the cool down animation finishes. In Melee, for example, Marth's down tilt involves poking forward with his sword, which produces a hitbox, then retracting the sword, which takes a significant amount of time. Since IASA frames begin during the retracting animation, Marth can interrupt this animation with another action, such as a second down tilt. In tournament level play, Princess Peach's Vidjo-cancel and Vidjo-drop techniques make use of IASA frames.
Brawl introduced the concept of "selective IASA", whereby some attacks can only be interrupted by specific other actions, and the initial may partially continue at the same time. This prevents double jump cancelling, among other things.
External links