- pixels of different sizes
- rotating (!) pixels
- scaling pixels
- smooth gradients with millions of colours
- dynamic lighting overlayed on top
... I could go on :(
In one category it’s about retro authenticity and these games are defined by the fact that their final buffer is the same low resolution as their art. They also often feature limited palettes, especially ones that were actually used on retro consoles.
There’s also a second category of pixel art, where the style is more modern. The art is still low res, but the final screen buffer is high res. This is where you’re more likely to see stuff like smooth rotating sprites and lighting effects.
You may have a preference for one style or the other, but neither style is bad or “wrong”. Most people who use the modern style are doing it on purpose. There are fantastic looking games in both categories.
I surveyed the indie-game landscape a couple of years back, specifically looking for games in your first category, but struggled to find any recent examples. 2D transforms, alpha-blending and lighting effects seem to be the standard now.
Loop Hero is strict about its pixel art and uses a fixed 16-colour palette that is reminiscent of the Commodore 64.
Baba Is You has visuals that you could basically render on a ZX Spectrum.
And in addition to doing pixel art well, these are all pretty great games.
(Although I would consider a low-res limited-palette game which uses transparency, lighting, rotation, scaling and other transforms as retro since that was already possible decades ago.)
I (and many others) think mismatched pixel sizes look bad, but that there's nothing inherently wrong with those other things.
In such a world, rotating a pixel sprite by 45 degrees should just look like there being multiple invisible “grids” to the world, each rendered at infinite resolution and downsampled to your display, where the sprite isn’t rotating per se, but rather the pixel grid “layer” the sprite is on (i.e. the hi-res texture the sprite layer is being rendered onto for compositing) is itself rotating.
Of course, if you’re going to use things like rotation/scaling, sub-pixel particle effects, 3D, etc. then you then either have to embrace it in your game setting’s art design everywhere so particular uses of it don’t stick out; or you have to acknowledge that any uses of it are basically “non-Euclidean geometry” from the viewpoint of in-setting observers, and thus slide your game’s mood toward something approaching either science-fantasy (e.g. Fez) or horror (has anyone done a Flatland Cthulhu game yet?)
Also note that “multiple distinct pixel grids” isn’t even unprecedented in retro games, either; there were plenty of consoles where you got one resolution for your tile map and a different (usually higher) resolution for your sprites; where sprites could sit on top of tiles in non-aligned positions. A few consoles and arcade cabinets even combined pixels with vectors!
But the real answer is they aren't inherently bad. People don't actually need it to conform to the past limitations. More that they want it to feel authentic to the nostalgic memory they have in their head.
For example, games like Shovel Knight go for an 8bit style, but they're not limited to an 8 bit color space, NES sprite limitations, etc.
A post from the author about the remade art: https://la-mulana.com/en/blog/graphic_full_remake.html
Compared to the art from the screenshots on Wikipedia: https://en.m.wikipedia.org/wiki/La-Mulana
https://www.gamedeveloper.com/design/breaking-the-nes-for-sh...
Adding lights from a lighting engine over the top of sprites with baked shading, might make a pretty image but it is not pushing pixel art forwards. Scaling and rotating can produce poor quality sprites.
P.s. Ashford is the best.
There's something to limited color space that those people do not seem to understand, be it the ones saying such critique, or the ones getting mad at it. We see color quantization in any realistic painting after the renaissance. Limiting the color space actually makes the pixel art look more realistic, because then every shade or shadow fits the overall drawings. Once you go Stardew Valley, sure it's pixel art, but just like a Picasso is great, it's not a Caravaggio, it's not "realistic" when it comes to how lighting reflects off surfaces.
Then there's the use of tiles/repeating background parts or having a full canvas where every pixel is unique. Although it's nice to look at, there's just too much information for the brain to process. That kind of art is nice, but in a game it's distracting. I personally call that kind of art pixel paintings and separate it from classic pixel art with tiles and limited colors.
It might be all just rose tinted glasses of nostalgia, but I firmly believe there's some science to what I just described. Look at any Caravaggio painting but especially portraits to see how limited the color space really is, how sometimes he uses shades of a color to give the impression of a very distant (color-space-wise) second color. It's really about that.
'Enter the Gungeon' is one example of that. The lighting adds atmosphere, doesn't harm the pixel art, and it's not distractingly over-the-top.
I've worked on a game which aimed for authentically retro pixel art, but in hindsight I think it was a silly misallocation of resources. There's a reason it's so uncommon nowadays. If I were to try again, I'd at least include high-resolution 2D transforms in the engine, and possibly dynamic lighting too.
I briefly explored the possibility of developing a style-preserving realtime rotation algorithm for sprites, but it's a hard problem.
The problem is that most indie games render at 2x or 3x or more natively.
Artistic preferences are subjective, but I expect most players would find that rotated sprite unappealing. This is especially true when the rotation is animated - the aliasing causes a distracting, staticky, random-noise effect which gives the impression that the sprite's fine details are chaotically changing. It's almost the aesthetic opposite of what most pixel artists are aiming for.
That’s the reason why some games use versions of the rotated sprites that have been tweaked by hand. See also tools like RotSprite (http://info.sonicretro.org/RotSprite).
I dislike lighting though (unless it's implemented tastefully) and I think normal maps look absolutely disgusting in any situation.
E: Also, overuse of shaders is discouraged. Especially non-pixel effects like blurring.