Pixel art is a large part of the legacy of game development. Every Pokemon game up until their X/Y series was rendered entirely with pixel art, Ragnarok Online (2000) was one of the first commercial works to feature 3D rendering along side pixel art characters. Even when early games tried to push the limits of 3D rendering such as Doom or Quake, they relied on Pixel Art based billboards to render their characters.
Limitations & Guidelines
Colors have 4 channels, R, G, B, and Alpha (transparency), and most modern devices use an 8 bit per channel (for a maximum of 256 possible brightness levels per channel) for image files and displays. On old game consoles like the Gameboy, Super Nintendo, Genesis, and even the GBA, developers had to deal with tighter color requirements. The Gameboy only had 4 shades to choose from, the Gameboy Color had a 5-bit (for a max of 32 possible brightness levels) per channel display, and could display a maximum of 56 colors, though normally it was far less. Pixel art was born from these limitations.
In addition, older devices had limited amounts of ram. The Commodore 64’s resolution was 320 by 200 pixels, and so if you wanted a 4 bit display, you would need 4 bits for every pixel (64,000) on the screen, for a grand total of ((64000 * 4)/8)/1000 = 32kb of ram, which was often times more than the amount of ram in the entire computer!
In addition, on the Nes, sprites were very small images, so often times you would be limited by the size a sprite could be, constrained to a 8x8 grid. You could only have 64 of these sprites on a screen at any given time.
We’re now free to use all 256³ colors if we want, make pixel art at any size, but bear in mind restrictions are what makes pixel art distinct from other forms of art. Even to this day we have places like PixelJoint keeping these restrictions alive.
Pixel Art Vs. Digital Paintings
Pixel Art is an image that was designed pixel by pixel.
It’s different from other forms of art like digital painting or line art in that every pixel is important, whereas those forms of art avoid that level of precision.