The ADD system is focussed on the most basic level of move difficulty. There is much more to the analysis and terminology used in advanced freestyle footbag that pure ADDs. Some of the concepts are below. Note that not all terminology is agreed upon or used the same way throughout the sport; your mileage may vary. But these descriptions will hopefully help explain some of the concepts in common use today.
“Paradox” (pdx) is a term that applies to moves that have an extra body add due to a dexterity that is harder to do because of the set (which in the original add system is not supposed to be possible, hence the “paradox”).
Symposium (Symp) is a concept for moves where the leg performing a dexterity is planted immediately before and after the dexterity, while the other (setting) leg does not touch the ground.
Symposium moves include:
Symposium is a Body concept that only applies to Dexterities. However, not all dexes are elligible for the symposium ADD. This is due to the fact that in some moves, the leg that does the dex is also the one that does the delay. When a move that cannot be symposium is done in a symposium style, it’s called symple. Dexes that can be symposium can also be done in a symple style, but symple never receives an ADD.
The [Butterfly] is also never symposium, only symple.
“Rooted” is when a move is ended with the delaying foot planted. “Rooting” is when a set is begun with the bag stalled on the foot that’s on the ground. When Uptime Dexterities are done from a rooted position, they are called anti-symposium.
“Stomping” is a concept that involves planting both feet at once after setting the footbag, then executing the desired move. An example of this would be a “Stomping double leg-over” (Set -> Stomp -> Double leg-over).
“Waxing” is when extra steps are put into moves.
Crispy and Original
“Crispy” is a concept used to describe a move using an uptime set, wherein the “Original” version does the same dexterity mid- or down-time. For example, a cripsy eggbeater would be an atomic legover.
X-Dex is an unofficial concept, because it has yet to be accepted by the IFPA as part of the official Rules of Footbag Sports. However, it is in common usage within the advanced freestyle community today.
X-Dex is similar to the symposium and paradox concepts above — it is a dexterity add that represents the added difficult of certain types of dexterities. In the case of X-Dex, the added difficulty involves a complete “circling” of the footbag in the context of any move (as opposed to most dexterities, which are not really forcing the player’s leg/foot to completely circle the bag).
For example, after two full dexterities (e.g., double around-the-world) are completed, the difficulty of doing the first dexterity was much greater than for a single around-the-world.
Thus, X-Dex represents the additional degree of difficulty of doing a “full” dexterity.