In a 2d beat em up, every character is like a flat piece of cardboard, characters aren’t square or circular, they’re more like a line drawn on the ground projected upwards. moves aren’t high or low or mid, they’re all a line projected a fixed distance in front of the character. More than that, the characters can never face backwards in any way. They don’t have 8, 6, or even 4 facing directions, they have two. They can only attack two ways, forward or back, and all their attacks only vary in startup time and strength. They can’t attack across the Z axis at all. Even though 2D beat em ups allow jumping, the lack of spatial dynamic in the rest of the game makes the application of these jumps limited where a game like Ys Origin or Oracle of Seasons can actually have a semblance of aerial combat.
In a 3d brawler game, you can fully move around the 3d environment, the character can attack in any direction and face in any direction. the attacks are capable of having specific hitboxes rather than being a projection of a line stemming off a projection of a line.
Virtua Fighter and Tekken let you move back and forth in 3d space in addition to this, and have moves that sweep across or track the person left, right or both.
The trouble is, this is still kind of a shallow 3 dimensional interaction, rather than it being relative to 360 degrees of possible rotation, you have kind of a left/right/mid thing in addition to the full 2d plane. However when you move into a behind the shoulder type of 3d camera, a common occurrence is you get these lock-on systems, like in the DBZ fighters, or Rise of Incarnates (some shitty PC soul calibur spinoff I played the alpha of) where everything is perfectly locked onto the opponent. Imagine if in a 3d fighter every single move had full left/right tracking, there would be no point in making it 3d or having side-stepping anymore because everything effectively exists everywhere on the Z axis. Extreme lock-ons in behind the shoulder type of fighting games have a similar effect, it converts a 3d game into a 1d game.
Like, compare to Dark Souls, that game’s combat ends up being mostly 2d, because there’s almost no jumping in the middle of combat, especially not over people’s attacks, and there’s almost no ducking under attacks either except in extremely rare situations, there’s also a lockon system, which makes it so you always face your opponent, so dark souls is ALMOST a 1d game in that similar way (barring like terrain shenanigans), but characters become unable to rotate when they start swinging their weapon, so in that short period of time you can move around them. This is why a lot of dark souls matches end up being circle strafing, because if someone swings, the other guy moves around it while one is locked on. So it adds this great dynamic to sometimes not lock-on, and instead free-aim the direction of your slice, making dark souls slightly more 2d than it would be otherwise. In multiple enemy combat, you of course have multiple enemies all in different positions, so that’s very 2d.
Here’s a picture I just drew up. I didn’t have time to include examples like DBZ, Dark Souls, Naruto, or Chivalry. (Also those are harder to draw with good perspective.)
What I really want to see is someone conquering the whole 3d fighting game thing (not because current fighters are insufficient, but because it would be interesting in its own right), to make a fighting game in full 3d where all the hitboxes matter and you can have that intense level of articulation, but that’s a very tricky thing to do from a control standpoint. I think Chivalry really comes closest to that type of ideal, but it’s simple and awkward in a lot of ways. Blade Symphony works in a similar vein, but both have a weak type of counterplay compared to what you get in traditional fighters and that’s a tricky design problem to solve on PC. DMC or Bayonetta would run into a similar problem if it were made multiplayer, along with the lock-on being too accurate, you’d have to introduce more moves that shoot off into the diagonals or sides to really take advantage of all the space around the players, having them avoid things on the 2d plane that is the ground, as well as try to diversify the block zone thing, because you block omni-directionally, which is lame.
In DMC though, you’d at least get away from the lock-on problem in the up-down thing, like when people jump, because characters don’t angle their attacks upwards or downwards like in DBZ or rise of incarnates. So you can go over other people’s attacks by jumping over them, so you get 2D gameplay on a plane composed of the distance to the other player, and your height. Only Chivalry has distance on both axes, and height involved so far.
Here, I ended up drawing a picture to try to illustrate my point.