Corey Johnson a8717733ba docs: add README and CLAUDE.md, use Pico dropdown for image picker

- README: API docs, usage example, dev tool instructions
- CLAUDE.md: architecture notes on Hono JSX, Pico CSS, implementation details
- Image picker now uses Pico's <details> dropdown pattern

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

2026-01-06 16:37:21 -08:00

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tiny-sprites

See README.md for the API and usage documentation.

Architecture

Hono JSX (not React)

This project uses Hono's JSX implementation, not React. Key differences:

Server-side: hono/jsx for the Sprite component (renders to HTML strings)
Client-side: hono/jsx/dom for the dev tool UI (renders to DOM)
No hooks: The Sprite component is pure server-side JSX with zero client JavaScript. No useState, no useEffect. The dev tool uses vanilla JS with a simple mutable state object and manual DOM updates via render() calls.

Dev Tool Styling

The dev tool uses Pico CSS for styling:

Classless styling - semantic HTML gets styled automatically
<details class="dropdown"> for the image picker (native open/close, no JS needed)
CSS variables like var(--pico-primary-background) for theming

Interesting Implementation Details

CSS Variables in @keyframes: Instead of generating unique keyframes per sprite, we define one global keyframe that uses CSS custom properties:

@keyframes sprite {
  from { background-position: var(--x) var(--y) }
  to { background-position: var(--ex) var(--y) }
}

Each sprite just sets --x, --y, --ex as inline styles. This avoids dangerouslySetInnerHTML entirely.

Frame Detection Algorithm: The analyzer (src/dev/analyze.ts) scans pixel columns to find content regions. It requires a minimum 10px gap between regions to count as separate frames - this handles sprites that have internal empty columns within a frame.

Crop Calculation: For each frame, we find the bounding box of non-transparent pixels, then union all frames' bounds. This gives a consistent crop that works across all animation frames without the sprite "jumping".

Canvas Pixel Analysis: We draw the image to a canvas and use getImageData() to read pixel alpha values. The alpha byte is at index (y * width + x) * 4 + 3 in the flat pixel array.

Default to using Bun instead of Node.js.

Use bun <file> instead of node <file> or ts-node <file>
Use bun test instead of jest or vitest
Use bun build <file.html|file.ts|file.css> instead of webpack or esbuild
Use bun install instead of npm install or yarn install or pnpm install
Use bun run <script> instead of npm run <script> or yarn run <script> or pnpm run <script>
Use bunx <package> <command> instead of npx <package> <command>
Bun automatically loads .env, so don't use dotenv.

APIs

Bun.serve() supports WebSockets, HTTPS, and routes. Don't use express.
bun:sqlite for SQLite. Don't use better-sqlite3.
Bun.redis for Redis. Don't use ioredis.
Bun.sql for Postgres. Don't use pg or postgres.js.
WebSocket is built-in. Don't use ws.
Prefer Bun.file over node:fs's readFile/writeFile
Bun.$ls instead of execa.

Testing

Use bun test to run tests.

import { test, expect } from "bun:test";

test("hello world", () => {
  expect(1).toBe(1);
});

Frontend

Use HTML imports with Bun.serve(). Don't use vite. HTML imports fully support React, CSS, Tailwind.

Server:

import index from "./index.html"

Bun.serve({
  routes: {
    "/": index,
    "/api/users/:id": {
      GET: (req) => {
        return new Response(JSON.stringify({ id: req.params.id }));
      },
    },
  },
  // optional websocket support
  websocket: {
    open: (ws) => {
      ws.send("Hello, world!");
    },
    message: (ws, message) => {
      ws.send(message);
    },
    close: (ws) => {
      // handle close
    }
  },
  development: {
    hmr: true,
    console: true,
  }
})

HTML files can import .tsx, .jsx or .js files directly and Bun's bundler will transpile & bundle automatically. <link> tags can point to stylesheets and Bun's CSS bundler will bundle.

<html>
  <body>
    <h1>Hello, world!</h1>
    <script type="module" src="./frontend.tsx"></script>
  </body>
</html>

With the following frontend.tsx:

import React from "react";
import { createRoot } from "react-dom/client";

// import .css files directly and it works
import './index.css';

const root = createRoot(document.body);

export default function Frontend() {
  return <h1>Hello, world!</h1>;
}

root.render(<Frontend />);

Then, run index.ts

bun --hot ./index.ts

For more information, read the Bun API docs in node_modules/bun-types/docs/**.mdx.

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