Stale-Move Negation is an element present in Super Smash Bros. that was introduced to Super Smash Flash 2 in v0.6. Whenever the player lands an attack, the strength of said move decreases. The more frequently a certain attack hits within a certain frame of reference, the weaker it will be. This is meant to encourage the player to use and explore the character's whole moveset instead of relying on using the same attacks excessively.
To calculate the staleness of any move, a queue is used. Whenever the player lands an attack, it is added to this queue; up to nine moves can be stored in it during a match. The most recently used moves will have a larger damage penalty, while older attacks that are still on the queue will be barely affected. If an attack is not on the queue it's referred as being "fresh".
Any attack can be in the queue multiple times and can even occupy all the spots. If this happens, the move will do approximately 45% of its original damage.
When the same attack hits more than one character, it's added the same number of times to the queue as the number of players it hit, regardless of which hitbox of that move connected. Similarly, each hit of a multi-hit move will stale the attack, effectively making later hitboxes weaker. While this may seem as a drawback for this type of attacks, it can also help to unstale other moves by quickly filling the queue with just one attack. Finally, all charge levels of a smash attack share the same staleness.
Unlike regular attacks and the official games' special moves, in Super Smash Flash 2 special moves have some different mechanics to those described above:
- Any non-projectile special move started while airborne counts as a different move to their grounded counterparts (they don't share the same staleness).
- Unlike smash attacks, charge levels of any non-projectile chargeable special move will not share the same staleness.
- Projectile special moves can only stale once per time thrown; if it's a multi-hit move or hits more than one opponent, it still will only be added once to the queue.
Items also have unique properties; while battering items do get stale (and share a universal staleness), any item when thrown will not be added to the queue and as such will always do the same damage. This also applies to items produced by characters themselves, such as Link's bombs or Peach's turnips.