neon-survivors/tools/gen-icons.js

// Generates PWA icons without external deps: neon diamond on dark bg.
'use strict';
const zlib = require('zlib');
const fs = require('fs');
const path = require('path');

function crc32(buf) {
  let table = crc32.table;
  if (!table) {
    table = crc32.table = new Uint32Array(256);
    for (let n = 0; n < 256; n++) {
      let c = n;
      for (let k = 0; k < 8; k++) c = c & 1 ? 0xEDB88320 ^ (c >>> 1) : c >>> 1;
      table[n] = c >>> 0;
    }
  }
  let c = 0xFFFFFFFF;
  for (let i = 0; i < buf.length; i++) c = table[(c ^ buf[i]) & 0xFF] ^ (c >>> 8);
  return (c ^ 0xFFFFFFFF) >>> 0;
}

function chunk(type, data) {
  const len = Buffer.alloc(4);
  len.writeUInt32BE(data.length);
  const t = Buffer.from(type, 'ascii');
  const crc = Buffer.alloc(4);
  crc.writeUInt32BE(crc32(Buffer.concat([t, data])));
  return Buffer.concat([len, t, data, crc]);
}

function png(w, h, rgba) {
  const stride = w * 4;
  const raw = Buffer.alloc((stride + 1) * h);
  for (let y = 0; y < h; y++) {
    raw[y * (stride + 1)] = 0;
    rgba.copy(raw, y * (stride + 1) + 1, y * stride, (y + 1) * stride);
  }
  const ihdr = Buffer.alloc(13);
  ihdr.writeUInt32BE(w, 0); ihdr.writeUInt32BE(h, 4);
  ihdr[8] = 8; ihdr[9] = 6;
  const sig = Buffer.from([0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A]);
  return Buffer.concat([
    sig,
    chunk('IHDR', ihdr),
    chunk('IDAT', zlib.deflateSync(raw, { level: 9 })),
    chunk('IEND', Buffer.alloc(0))
  ]);
}

function lerp(a, b, t) { return a + (b - a) * t; }

function makeIcon(size) {
  const px = Buffer.alloc(size * size * 4);
  const cx = size / 2, cy = size / 2;
  const maxD = Math.hypot(cx, cy);
  const diaR = size * 0.34;
  for (let y = 0; y < size; y++) {
    for (let x = 0; x < size; x++) {
      const i = (y * size + x) * 4;
      const dx = x - cx, dy = y - cy;
      const d = Math.hypot(dx, dy) / maxD;

      // background: vertical dark gradient
      let r = lerp(10, 5, y / size);
      let g = lerp(10, 5, y / size);
      let b = lerp(31, 12, y / size);

      // soft purple glow ring
      const glow = Math.max(0, 1 - d * 2.2) ** 2;
      r += 124 * glow * 0.35; g += 92 * glow * 0.35; b += 255 * glow * 0.4;

      // neon diamond
      const ad = Math.abs(dx) + Math.abs(dy);
      if (ad < diaR) {
        const t = ad / diaR;
        // gradient edge cyan -> center violet -> white core
        if (t > 0.82) { r = 224; g = 250; b = 255; }          // rim highlight
        else if (t > 0.55) { r = 0; g = 229; b = 255; }        // cyan edge
        else if (t > 0.25) { r = 124; g = 92; b = 255; }       // violet body
        else { r = 233; g = 213; b = 255; }                    // white core
        // subtle scanline shading
        if (((x + y) >> 3) % 2 === 0 && t <= 0.82) { r *= 0.92; g *= 0.92; b *= 0.95; }
      }
      px[i] = Math.min(255, r | 0); px[i + 1] = Math.min(255, g | 0);
      px[i + 2] = Math.min(255, b | 0); px[i + 3] = 255;
    }
  }
  return png(size, size, px);
}

const outDir = path.join(__dirname, '..', 'icons');
if (!fs.existsSync(outDir)) fs.mkdirSync(outDir);
for (const s of [192, 512]) {
  const f = path.join(outDir, `icon-${s}.png`);
  fs.writeFileSync(f, makeIcon(s));
  console.log('wrote', f, fs.statSync(f).size, 'bytes');
}