Earthbound Battle Background JS is exactly what its name implies: the battle backgrounds from the SNES RPG Earthbound/Mother 2, rendered entirely in client-side JavaScript.
For more information, see the project's README and source code. You might also like the Android Live Wallpaper version.
Every battle background is composed of two layers, each with 327 possible styles (including "blank"/zero). The layer styles can be interchanged, such that Layer 1: 50 and Layer 2: 300 is the same as Layer 1: 300 and Layer 2: 50. Thus, there are C(n,r) = 52,650 possible different background combinations. Obviously, this many don't exist in the game--the SNES's graphical capabilities only allow it to properly render 3,176 of these combinations, and of those, only 225 are ever used.
The data for each of the 327 styles is bundled within the SNES cartridge. Tiles are constructed from various memory addresses in Earthbound game data. Each background also has its own distortion effect.
For a list of every possible background, visit this link.
It's pretty damn hard to find out which battle backgrounds correspond to which enemies. You can review the list of enemies matched with known battle backgrounds to try and get your favorite on the Suggested Layers option. If you discover a new one, please, make a pull request and I'll add it to the list, giving you full credit!
Because it can.
If you happen to know Shigesato Itoi, tell him about this! I'm a huge fan of his work.
About three years ago, Mr. Accident of forum.starmen.net provided me with the original battle background generation code, which was a C# project that uses the battle backgrounds as Windows screensavers. He also provided me with help along the way, and as far as I'm aware, he discovered the math behind it all, including the entire Offset function calculation. This port would be nothing without him.
After that, I created the Android live wallpapers in 2010. I worked on this JavaScript version off and on throughout 2013, and finished it in mid-December.