By itself, Art of Fighting/Ryuuko no Ken introduced more things to the fighting game genre that are considered standard, or at least interesting, than almost any other series:
Supers (“super death blows”)
In AoF1’s story/arcade mode you had to unlock these moves in a bonus game, an option you only got after beating your first 2 opponents, but it was there. Once you used the move, it looked and felt significantly more powerful than your regular specials:
The Haohshokoken super projectile was so huge that it was practically unavoidable, and even if blocked it would take a noticeable chunk from the opponent’s life bar. In return, it ate up practically all of your power bar.
And since you had to perform the motion correctly a few times to be able to unlock it, a few playthroughs let you figure out if it was within your reach, or if boosting your life or general power was a better use of your early bonus game attempts.
Some games give you a choice of supers, but not many let you pick “none of the above” and let you boost something else in exchange. Speaking of something you can boost…
Power bars (“spirit bars”)
Under the characters’ life bars you’d have another bar that would affect the moves available to you - this may be standard nowadays, but it wasn’t always so.The extra bar affected AoF more than it does most modern game, in that it wasn’t just for supers but was also consumed by the use of specials, which meant these had to be used carefully to make it count - a notion that appears to have been entirely dismissed during the past decade, where physics-defying attacks that do block damage in exchange for commands unguessable by beginners are treated like a part of the game that’s taken for granted by everyone else. In AoF, if you lack the power bar to use a special, it will either came out in a very weakened state or not at all, which means no fireball spamming for applicable characters, since that’s not sustainable over time (also, regular attacks can destroy projectiles if timed right). You’re better off mastering your basics, and leaving the specials for actual special occasions when their particular properties are an actual advantage. The bonus game that let you boost the bar consists on trying to chop off the top of a bunch of beer bottles, like Mr Miyagi in Karate Kid, further illustrating how unusual the abilities it powers are supposed to be and the focus they’re meant to require:
The bar starts out full each round, and slowly refills itself over time. It’s spent by using specials and supers, and by being taunted by the opponent. You can refill it manually with a charging command, and you can increase the bar’s maximum size in one of the bonus games. This bar is the heart of the series’ gameplay, and its effect on the use of specials to prevent over-reliance on some moves is something I’d like to see more often - instead of a standard “1 level of power bar = 1 super”, using different smaller fractions of a level of bar to pay for the use of some moves, and tweaking those values over time with patches if needed is something I could get behind.
As mentioned above, these were used to drop an opponent’s power bar - to break their concentration, so to speak. Doing so at the right time could not only be the difference between an opponent being able to threaten you with a move that could counter your tactics, it could also annoy him in general - other series would mostly stick to the 2nd use in their own implementations (meaning it’s practically never used in an actual fight in those), but it was nice to have the option of the 1st one.
It was also a nice way to provide a bit of characterization to characters outside stuff like victory poses, endings, stages and limited dialogue, which were among the very few sources of lore in the genre back in the day. Dan Hibiki’s reputation exists because of this.
“Super supers” (“desperation move”)
They could have settled for inventing supers and be pleased with themselves, but then that would just be an maximum power special. SNK didn’t settle for that.
AoF was a fighting game, but it was also a story, and a story could always use a few dramatic moments. Snatching victory from the jaws of defeat with a desperate special attack that only works when your life is really low and consumes all the power bar you should have probably used to avoid reaching that point sounded dramatic enough to them. The Haohshokoken, however, was a projectile you first use in the controlled environment of a dojo against a distant and stationary target before you get to use it on opponents - it’s nice to have, but had its limits as a dramatic battle event, so an entirely different move was made for the occasion: a dash into just about every regular move the character had unleashed at an incredible speed - the Ryuuko Ranbu.
In later games of the series different characters would have other very different moves for the same circumstances. In AoF3 beating a character with this move or its character-equivalent would decide the fight - the Ultimate KO feature, meaning if you won a fight using it in round 1 there would be no round 2, since the move was meant to be so overwhelming - this particular feature never returned in any games I’m aware of, which is understandable - it destroys the possibility of a comeback off a match that must have been pretty close, but it was interesting that they decided to try it anyway… something perhaps best left for single-player games, but nowadays most story modes in the genre only make you fight 1 round per character anyway (the MK9 fails at this and many other things in its story mode, despite all the praise rained on it).
It was also a nice way to make use of the game’s zoom feature, if you started the move some distance away, as it would proceed into a nice view of the aggressor and victim’s pretty huge sprites, so speaking of which…
Back when fighting games were strictly in 2D there was a bit of a conflict between graphical detail and functionality, especially when projectiles and other aspects involving distance were involved - enough space to move freely and the sprites can’t be too big, make them too big and you’re practically fighting in a phonebooth. SNK was all like “why not both?”, and made huge incredibly detailed sprites, detailed enough to see bruises on the characters’ faces if they were hit hard and often enough, and used their hardware’s abilities to just zoom everything out if the characters moved away from each other. It did the trick nicely before 3D brought concerns like camera angles to the genre, and even if AoF’s implementation wasn’t the best, it paved the ground for that and other games that followed, both from its own company as well as the competition’s - this applies to a lot of what this game did, really.
Projectile abuse prevention
I already mentioned the power bar limiting the overuse of projectiles, but it can’t be overstated that SNK’s finest efforts always had some way to prevent projectile-based characters from dominating: Fatal Fury had the place shift system, in Samurai Shodown most projectiles required the use of weapons (which could be lost) and some projectiles could be cut with weapons mid-flight, King of Fighters had dodges and rolls, and SvC Chaos failed in part because it had neither, like the competition it tried to do justice to. Like I said, the power bar meant if you tried projectile spamming your way through a match, you’d soon run out of power to do so. Additionally, projectiles could be destroyed with a properly timed attack like a regular jab, long before parrying came along in SF3. Beginner Ryus would find themselves in need of learning their basic moves under this game’s rules.
A balance between action and story
The NeoGeo was both an arcade and home console system, so it had to walk a fine line to cater to both environments - while the arcade focuses on the action, with its owner preferring to see players spend their time trying not to lose so they’ll spend more money, the home environment allows for a more contemplative attitude, which is why narrative-heavy genres like RPGs thrive in it.
AoF took on the challenge, even if it meant going for a classic plot device:
But that was just the part that was visible in-game:
Within that limited frame, SNK did a fair amount with the genre for its time:
It told you the plot in the opening
Mentioned South Town in that opening, connecting it to Fatal Fury
Added dialogue before each fight, providing a little world-building from that dialogue, the information you extracted from defeated opponents and the protagonists’ musings as they traveled between them
Included that infamous ex-secret of King’s which still echoes into KoF XIII
Left a cliffhanger in the ending for the following game.
And in that following game, Art of Fighting 2:
South Town was given an even bigger map that included the old one
Every character had dialogue against every other character, with body language to match that was only ever used in those scenes
Ultimately it was revealed that the game took place a decade before Fatal Fury by showing us a young Geese while he was still working for the police, hinting at an off-screen story of his own - not to mention you could see his men in suits spying from corners in just about every stage in the game.
Lots of information with minimal interruption in the action.