earthbound-battle-backgrounds-vite

This project acts as a library to render Earthbound's battle backgrounds. You can render the results in a browser or even on the server.

This fork is an updated version of kdex's original library. I first migrated the codebase from Webpack to Rollup for performance and smaller bundle sizes, and later to Vite for future-proofing.

What is this?

Earthbound, also known as Mother 2 in Japan, is a SNES game released in 1994. This project displays Earthbound's battle backgrounds. In order to render the frames, currently a Canvas 2D context is used.

import { BackgroundLayer, Engine } from "earthbound-battle-backgrounds-vite";

/* Create animation engine  */
const engine = new Engine([new BackgroundLayer(153), new BackgroundLayer(298)], {
    canvas: document.querySelector("#target-canvas")
});
engine.animate();

API

There are two exports in the package, namely BackgroundLayer and Engine.

BackgroundLayer

constructor(entry)

Description

Creates a new BackgroundLayer displaying entry.

Signature

• entry: number

The index of the layer to render. It is bounded by BackgroundLayer.MINIMUM_LAYER and BackgroundLayer.MAXIMUM_LAYER.

Engine

constructor(layers, options)

Description

Constructs a new Engine, which can be used to render BackgroundLayers.

Signature

• layers: Array<BackgroundLayer> (default: [])

The array of BackgroundLayer instances to render.

• options: object

An object containing rendering options.

• options.fps: number (default: 30)

The framerate to render with.

• options.aspectRatio: number (default: 0)

The aspect ratio to render with.

• options.frameSkip: number (default: 1)

The engine is time-dependent and uses an internal clock that will be incremented after each frame. This number decides by which constant the clock is incremented.

• options.alpha: Array<number> (default: Engine.computeAlphas(layers.map(layer => layer.entry)))

An array that specifies the opacity for each BackgroundLayer in layers. The default is to give each layer the same opacity so that all alphas sum up to 1. Layer 0 is ignored, as it does not display anything.

• options.canvas: CanvasElement (default: document.querySelector("canvas"))

The canvas element to render to.

static computeAlphas(entries)

Description

Computes an array of alpha values so that every valid layer gets the same opacity.

Signature

• entries: Array<number>

An array where every number must be a number must be at least BackgroundLayer.MINIMUM_LAYER, and at most BackgroundLayer.MAXIMUM_LAYER.

rewind()

Description

Resets the internal engine timer to 0. This will cause all BackgroundLayers to be rendered in their initial state.

Signature

Nullary.

animate()

Description

Runs the engine. This will cause frames to be drawn on the instance's canvas.

Signature

Nullary.

Project maintenance history

• In 2008, the code for this project started out on PK Hack as a Windows screensaver, written in C# by Mr. Accident. Mr. Accident's source code has been published here.
• In 2010, gjtorikian ported Mr. Accident's Windows screensaver from C# to Java to support Android Live screensavers.
• In 2013, gjtorikian ported his own project from Java to ECMAScript 5 to support all devices with a web browser. He is well aware that his port is terrible (in fact, he even wrote a dedicated section in his README.md, just to reflect that).
• In 2016, kdex rewrote the latter in ES2015+ for it to stay maintainable.
• In 2017, gjtorikian copy-and-pasted kdex's source code into his repository.
• In 2021, I updated the codebase to use Rollup and removed/replaced some old dependencies to keep the project maintainable as was kdex's vision.
• In 2025, I migrated the codebase to Vite, continuing kdex's original vision for a maintainable project (kdex has since left GitHub).