The two (and a half?) sides of 2.5D - how to capitalize on depth

2.5D is one heck of a silly-ass term introduced in the PlayStation era to describe the 2D gameplay set in a 3D environment featured in games like Klonoa, NiGHTS into Dreams, and Kirby 64. More recently the term has been applied to Trine, New Super Mario Bros., 'Splosion Man, and dozens of others. It's a bit ironic - in the fifth generation, the 2D gameplay was conservative and the 3D graphics cutting edge, while in the seventh generation, it's the 3D visuals that are the norm and the 2D playing field that subverts expectations. Anyway, I mostly just said that to prove that I know what irony is, cuz no one does anymore. Even complaining about people not understanding irony has become cliche. How ironic.

See that time I used it wrong.

2.5D did exist in some sense before polygonal graphics - I'd say it's not too much of a stretch to say that parallax scrolling (Moon Patrol, Sonic the Hedgehog) is its predecessor. Parallax similarly strives to 

Man I just had to go bitch out Wikipedia for the terrible article it has on 2.5D. Don't go there, it's ugly. The page looks like a Frankenstein's Monster of unrelated articles on isometric graphics and pseudo-3D with a teeny tiny paragraph acknowledging actual 2.5D games as we know them today. If you do go, make sure to check out my bitchin' takedown on the Talk page. See, I'm an armchair armchair Wikipedian. That is to say, one can edit Wikipedia without getting out of their seat. But I don't even do that much. I just yell on the Talk pages at the actual productive editors that they're doing it wrong. But seriously, who has time to do all that research? Let a monkey do it. Did you know that infinite monkeys given infinite cheeseburgers will inevitably produce the entire content and discussion pages of Wikipedia? This is a known scientific fact. The real question is: who's cooking the cheeseburgers? Or wait, by the infinite monkey clause, are the infinite monkeys also guaranteed to produce infinite cheeseburgers the same way they wrote Hamlet? In that case maybe it'd be easier just to do hamburgers.

Where was I? Goddamnit why did I stop mid-sentence for that? Okay. Parallax. Parallax scrolling is the adjustment of the scroll-rate of distant objects to create a 3D perspective using only 2D objects. You knew that though. When 3D models turned real, they became the preferred method for displaying 3D environments (shocking!), though 2.5D didn't really take off because 2D gameplay was simultaneously going out of vogue. With 2D's recent resurgence in popularity, 2.5D games are probably even more common than strict 2D, as these days 3D visuals are actually easier to make decent-looking on TVs than are 2D sprites.

2.5D is very popular with modern fighters

I've gotten into the bad habit of spending a few paragraphs just defining my terms and thus wasting a lot of time before getting to my actual point. It's because I don't know who the audience of this blog is. I want it to be accessible, but it's almost a prerequisite for interest in this discussion that you've played 2.5D games... in which case you likely already know what 2.5D is, so you don't need me to explain it. Hey looks like this is one of those articles with running commentary - sweet!

Even the most primitive 2D games use some approximation of 3D - any game with a backdrop has extended its world beyond a strict 2D plane. Super Mario Bros. shows us hills, clouds, and castles beyond our reach. The limitation of 2D is not a graphical one, but the very distinction between the field of play and the field of observation - traditionally, the foreground and the background. Tantalizing players with beautiful vistas and distant ruins can enhance their engagement with the world, so one of the great appeals of 3D gameplay is the ability to reach those places - the unification of the entire game world into a continuous, playable space. A player who is free in all [three] dimensions can strive toward that distant castle and everything else they see, limited only by real environmental boundaries like walls and cliffs. 2.5D offers a chance to bridge the gap between these modes - to use a two-dimensional field of play to span a three-dimensional space. While this keeps movement comfortably in the 2D realm, the plane of movement itself can wind through the third dimension.

Surprisingly, most 2.5D games do not capitalize on this opportunity. Games like Little Big Planet, New Super Mario Bros., and Donkey Kong Country Returns retain the traditional 2D distinction between background and foreground. 3D visuals endow the backgrounds with more depth than is achievable strictly in 2D, but the field of play remains as limited as ever. Check out an example from DuckTales: Remastered: 

Gameplay starts at 1:45. Observe all the background objects that Scrooge can never reach. The game takes place entirely on a flat plane parallel to the screen.

This type of game remains strictly left-to-right and is really just a visual upgrade (or downgrade, if you're of that opinion) to 2D. The player's involvement in the world isn't enhanced because the dissonance between playable and observable space is retained. Prepare for a mind-blowing MS Paint graphic I made to illustrate this type of world-thickening:

The distinguishing factor of this kind of 2.5D is the continuous depth of the background.

You can see that the only difference between 2D and this approach to 2.5D is a parallax-plus-one filling-in of empty space between layers - these are very much 2D games with 3D graphics. The camera still shows only one side of the action and the environment.

More ambitious 2.5D games take advantage of their 3D worlds to eliminate this wasted space. The 2D plane of play loops and twists through a logical 3D environment, allowing the player to fully explore (in a guided fashion) everything that they see. Check out the recent Castle of Illusion remake:

Gameplay starts at 0:20. Watch how Mickey's paths curve around to span the entire room.

This type of intertwining movement can also be seen in games like NiGHTS, Goemon's Great Adventure, and my personal favorite 2.5D game: Klonoa 2: Lunatea's Veil. Note how these - like full 3D games - only bound the player's exploration with physical barriers. There is an invisible dimensional limit on movement that forces a fixed left-right path through the world, but the end result looks like a trace of any given run of Super Mario 64 or Bubsy 3D. The camera moves along with these curved paths, keeping the player parallel to the screen - in doing so it swoops and rotates to show us many different sides of the game space. Back to MS Paint:

Convoluted image, but hopefully you can see I'm trying to represent that the plane of player movement bends within a fixed area. The camera angle at any given point can be represented by the normal vector of the plane.

The drawing in this post gives a different view of the same situation. We can see that, removing the presence of time, a 2.5D game like Klonoa is actually identical to a 3D game. Of course, we can't remove the presence of time (or at least, I can't - I don't know if I have any Tralfamadorians among my readership), so the experience is distinct. But it's also distinct from classic 2D, in that, although the gameplay could be spread out over a flat plane, the game world could not be flattened with it. 

The term 2.5D seems often to be considered a superficial distinction, as evidenced by its application to these two very different styles of presentation. While there is certainly no right/wrong, good/bad here, it seems clear to me that the latter Klonoa-derived category are indeed games attempting to bridge the gap between 2D and 3D, while the former are just glorified 2D. Don't get me wrong, I love 2D. But 2.5D has the potential to portray a space of greater depth and complexity, which expands the applicability of 2D gameplay to more realistic world models.