Decode/encode save files used by the game The Messenger

the_messenger_save_decoder.js

#!/usr/bin/env node

/*

If you run the script on an encoded file it will output a decoded file and
vise versa, because the action used to encode/decode is identical. The save
file format when decoded is plaintext JSON, which you can edit with your
favorite text editor.

You can find the save file at the following path. Please make a backup of the
file before you make any adjustments to it!

%userprofile%\AppData\LocalLow\Sabotage Studio\The Messenger\saveGame.txt

*/

const fs = require("fs");

if (process.argv.length < 4) {
	console.log("Required arguments: <inFile> <outFile>");
	process.exit(1);
}

const inFile = process.argv[2];
const outFile = process.argv[3];

function convertFile(inFile, outFile) {
	const data = fs.readFileSync(inFile, "utf-8").split("\r\n")[0];

	let convertedData = "";

	for (const char of data) {
		const charCode = char.charCodeAt(0);
		const isOdd = charCode % 2;
		const nudge = isOdd ? -1 : 1;

		const newCharCode = (charCode ^ 128) + nudge;

		convertedData += String.fromCharCode(newCharCode);
	}

	fs.writeFileSync(outFile, convertedData + "\r\n");
}

convertFile(inFile, outFile);

Hey @aqt thanks a lot for this tutorial. It helped a lot. Ive gotten it to work and I achieved the Achievement.
I wish you the best.