This game is notable for being the primordial to modern fighting games-- Specifically a somewhat anachronism to a game like Street Fighter 2. While many action//fighting games came after this one even The First Street Fighter, conceptually Yie Ar Kung-Fu has more in common with SF2 than SF1 does if we focus solely on mechanics and gameplay. I say this because of 'footsies.' A term that means almost anything, but generally we use it to describe a (usually) neutral situation where both players are establishing their own zones they control on the screen. It's a term that's gone through many different meanings because every game's "footsies" are incidental. It's purely just an emergent set of tactics one resorts to assess risk. The term 'footsies' wasn't strictly in regards to that-- It meant mashing cr.LK or-- "Duck Short" as Ryu or Ken in the earliest iterations of SF2. The 2 most immediate applications of this were:
Mashing this meant the opponent would be stuck in proximity guard if they tried walking back, which controlled their movement in some way and--
Their legs didn't have a hurtbox when doing this, so it was effectively a kind of force-field that limited engagement. The choices one might make to circumvent this ended up being grouped into that singular term.

Most fighting games before SF2 simply don't have 'footsies.' It's not irresponsible to say this. It mainly has to do with general placement of hitboxes, and the raw and intuitive nature of moving in and out- establishing your threat ranges and controlling the enemies own dimensions. Whether it be the air space or trapping them in the corner. That doesn't really happen in these games. There's no unit collision, attack feedback is generally poor-- And the hitbox detection isn't consistent or constant. That makes these games very button mashy and scrambley in a way that doesn't invite tactics aside from cheesy ones. Really, action titles like Castlevania 1 or Zelda 2 ended up being more of a real fighting game than SF1 or Violence Fight or the various games with 'karate' in their title. Credit where it's due though, these games were definitely necessary to learn from. And there are games-- like Urban Champion or Karateka that are both very memorable and innovated quite a lot. Urban Champion has a sway like motion, that quickly evades attacks. It also has dizzies, the first game to probably have both. Like, all of these games are REAL old, so there's a lot of instances where things taken for granted just don't seem to exist.

Yie Ar Kung Fu does definitely have some issues customary of fighting games of the time. Mostly relating to hit detection, but here's where it's different. In Yie Ar Kung Fu, you have 16 unique Normals. Accessed by holding or pressing either the punch or kick button and a specific direction. There are attacks that correspond to hitting the attack button and the opposite direction. What's novel is that for the time period, almost no other game featured individual movesets character to character. Now this isn't a head-to-head game, there's no real 2 player here. But in most games of this period the generic mob enemies featured the exact same set of moves as the player character. Those 16 Normals all have distinct use cases. Playing this game nowadays can feel a bit frustrating due to the abeforementioned hit detection problems-- But it's different in that there's a very clear design motivation in having you focus on the placement of your strikes; As well as the ebb and flow of the positioning between you and the enemy.

One look at the gamut of kicking moves you have will probably help illuminate it best. The most curious is the down-back kick move, which hits high while crouching, at a cost of horizontal reach in exchange for safety and controlling the zone directly above you. Each one of these hit at a very discrete location, and place your own 'hurtbox' back in particular ways. This is something unprecedented, especially for 1984. The various enemies all play with this in their own way. Some jump over to you to press the issue. Some throw projectiles (that you can hit for bonus points, very satisfying) at different elevations. All enemies have attacks that strike intentional High-Mid-Low zones you're meant to provisionally play around. Spacing and moving around anything these ai opponents do is very natural. You can bait certain responses by whiffing moves at specific ranges and then capitalizing on their own lost frames from whiffing-- trying to hit you. But you have to be careful, because the timing of this isn't easy, and it's still an ai opponent. Sometimes they just pick the right option anyways because they can.

Now it's not as extravagant as I might make it sound. This is still a highly experimental game from the 80s, with all the old game jank. The real kind, not the 'this game is too difficult' stuff. But mostly relating to technical issues, stuff I call 'mechanical pop-in' where things break down in a way that's really bizarre. Again, it's due to the hitboxes! But, this is why I love it.