diff --git a/shuffle.js b/shuffle.js
index c64485f..f371746 100644
--- a/shuffle.js
+++ b/shuffle.js
@@ -1,141 +1,183 @@
+//@ts-check
+'use strict';
 const fs = require('fs')
 const plist = require('plist');
 const assets = require('./assets.json')
 
-try {   // god-tier crash prevention system
-
-Array.prototype.shuffle = function() {
-    let length = this.length; let unshuffled = this; let shuffled = [];
-    while (shuffled.length !== length) {
-        let index = Math.floor(Math.random() * unshuffled.length);
-        shuffled.push(unshuffled[index]);
-        unshuffled = unshuffled.filter((x, y) => y !== (index))}
-    return shuffled;
-}  
-
-function plistToJson(file) {
-    let data = plist.parse(file)
-    for (let key in data.frames) {
-        let fileData = data.frames[key];
-        for (let innerKey in fileData) {
-            if (typeof fileData[innerKey] == 'string') {
-                if (!fileData[innerKey].length) delete fileData[innerKey]
-                else fileData[innerKey] = JSON.parse(fileData[innerKey].replace(/{/g, '[').replace(/}/g, ']'));
+/**
+ * returns a pseudo-random 32bit unsigned integer
+ * in the interval [0, `n`)
+ */
+const randU32 = (n = 2**32) => Math.random() * n >>> 0;
+
+/**
+ * https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
+ * https://github.com/steventhomson/array-generic-shuffle/blob/master/shuffle.js
+ * @param {any[]} a
+ */
+const shuffle = a => {
+    let len = a.length;
+    while (len > 0) {
+        const i = randU32(len);
+        len--;
+        [a[len], a[i]] = [a[i], a[len]]; // swap
+    }
+};
+
+/**
+ * get unique/distinct elements (same order)
+ * @param {any[]} arr
+ */
+const undupe = arr => arr.filter((x, y) => arr.indexOf(x) == y);
+
+/**
+ * convert plist string to JSON, then JSON to `Object`
+ * @param {string} file
+ * @return {import('plist').PlistObject}
+ */
+const plistToJson = file => {
+    const {frames: datFrames} = plist.parse(file);
+    // not using `Object.values`, because we want to mutate in-place
+    for (const out_k in datFrames) {
+        const fileData = datFrames[out_k];
+        for (const in_k in fileData) {
+            const fdik = fileData[in_k];
+            if (typeof fdik == 'string') {
+                if (fdik.length == 0) delete fileData[in_k]
+                else fileData[in_k] = JSON.parse(fdik.replace(/{/g, '[').replace(/}/g, ']'));
             }
     }}
-    return data.frames
+    return datFrames
 }
 
-if (!fs.existsSync('./pack')) fs.mkdirSync('./pack');
-
-function glow(name) { return name.replace("_001.png", "_glow_001.png") }
-function undupe (arr) { return arr.filter((x, y) => arr.indexOf(x) == y) }
-//function spriteRegex(name) { return new RegExp(`(<key>${name.replace(".", "\\.")}<\/key>\\s*)(<dict>(.|\\n)+?<\\/dict>)`) }
-let iconRegex = /^.+?_(\d+?)_.+/
-
-let forms = assets.forms
-let sheetList = Object.keys(assets.sheets)
-let glowName = sheetList.filter(x => x.startsWith('GJ_GameSheetGlow'))
-
-// newlines/CRs are usually present in text files, strip them out so they aren't part of the pathname
-let gdPath = process.argv[2] ?? fs.readFileSync('directory.txt', 'utf8').replace(/[\n\r]/g, '')
-
-if (!fs.existsSync(gdPath)) throw "Couldn't find your GD directory! Make sure to enter the correct file path in directory.txt"  
-let glowPlist = fs.readFileSync(`${gdPath}/${glowName[0]}.plist`, 'utf8')
-let sheetNames = sheetList.filter(x => !glowName.includes(x))
-let resources = fs.readdirSync(gdPath)
-
-let plists = []
-let sheets = []
-let glowBackups = []
-let glowSheet = plistToJson(glowPlist)
-
-resources.forEach(x => {
-    if (x.startsWith('PlayerExplosion_') && x.endsWith('-uhd.plist')) sheetNames.push(x.slice(0, -6))
-})
-
-sheetNames.forEach(x => {
-    let file = fs.readFileSync(`${gdPath}/${x}.plist`, 'utf8')
-    plists.push(file)
-    try { sheets.push(plistToJson(file)) }
-    catch(e) { throw `Error parsing ${x}.plist - ${e.message}` }
-})
-
-sheets.forEach((gameSheet, sheetNum) => {
-    let plist = plists[sheetNum]
-    let name = sheetNames[sheetNum]
-    if (!name.startsWith('PlayerExplosion_')) console.log("Shuffling " + name)
-    else if (name == "PlayerExplosion_01-uhd") console.log("Shuffling death effects")
-
-    let sizes = {}
-    Object.keys(gameSheet).forEach(x => {
-        let obj = gameSheet[x]
-        obj.name = x
-        if (sheetNum == sheetNames.findIndex(y => y.startsWith('GJ_GameSheet02')) && forms.some(y => x.startsWith(y))) {
-            let form = forms.find(y => x.startsWith(y))
-            if (!sizes[form]) sizes[form] = [obj]
-            else sizes[form].push(obj)
-        }
-        else {   
-            let sizeDiff = assets.sheets[name] || 30
-            let size = obj.textureRect[1].map(x => Math.round(x / sizeDiff) * sizeDiff).join()
-            if (name.startsWith('PlayerExplosion')) size = "deatheffect"
-            if (!sizes[size]) sizes[size] = [obj]
-            else sizes[size].push(obj)
-        }
+/** working directory */
+const wd = './pack/';
+
+try { // god-tier crash prevention system
+
+    fs.mkdirSync(wd, { recursive: true, mode: 0o766 });
+
+    const glow = (/**@type {string}*/ name) => name.replace("_001.png", "_glow_001.png");
+    //const spriteRegex = name => new RegExp(`(<key>${name.replace(".", "\\.")}<\/key>\\s*)(<dict>(.|\\n)+?<\\/dict>)`);
+    const iconRegex = /^.+?_(\d+?)_.+/
+
+    const
+        {forms} = assets,
+        sheetList = Object.keys(assets.sheets),
+        glowName = sheetList.filter(x => x.startsWith('GJ_GameSheetGlow'));
+
+    // newlines/CRs are usually present in text files, strip them out so they aren't part of the pathname
+    const gdPath = process.argv[2] ?? fs.readFileSync('directory.txt', 'utf8').replace(/[\n\r]/g, '')
+
+    if (!fs.existsSync(gdPath))
+        throw "Couldn't find your GD directory! Make sure to enter the correct file path in directory.txt"
+    let glowPlist = fs.readFileSync(`${gdPath}/${glowName[0]}.plist`, 'utf8')
+    const sheetNames = sheetList.filter(x => !glowName.includes(x))
+    const resources = fs.readdirSync(gdPath)
+
+    /**@type {string[]}*/
+    const plists = []
+    const sheets = []
+    const glowBackups = []
+    const glowSheet = plistToJson(glowPlist)
+
+    resources.forEach(x => {
+        if (x.startsWith('PlayerExplosion_') && x.endsWith('-uhd.plist'))
+            sheetNames.push(x.slice(0, -6)) // -6 removes ".plist", efficiently
     })
-    
-    Object.keys(sizes).forEach(obj => {
-        let objects = sizes[obj]
-        if (objects.length == 1) return delete sizes[obj]
-        let iconMode = forms.includes(obj)
-        let oldNames = objects.map(x => x.name)
-        if (iconMode) oldNames = undupe(oldNames.map(x => x.replace(iconRegex, "$1")))
-        let newNames = oldNames.shuffle()
-        if (iconMode) {
-            let iconList = {}
-            oldNames.forEach((x, y) => iconList[x] = newNames[y])
-            newNames = iconList
-        }
-
-        oldNames.forEach((x, y) => {
-            let newName = newNames[iconMode ? x : y]
-            if (iconMode) {
-                plist = plist.replace(new RegExp(`<key>${obj}_${x}_`, "g"), `<key>###${obj}_${newName}_`)
-                glowPlist = glowPlist.replace(`<key>${obj}_${x}_`, `<key>###${obj}_${newName}_`)
+
+    sheetNames.forEach(x => {
+        const file = fs.readFileSync(`${gdPath}/${x}.plist`, 'utf8')
+        plists.push(file)
+        try { sheets.push(plistToJson(file)) }
+        catch(e) { throw `Error parsing ${x}.plist - ${e.message}` }
+    })
+
+    sheets.forEach((gameSheet, sheetNum) => {
+        let plist = plists[sheetNum]
+        let name = sheetNames[sheetNum]
+        if (!name.startsWith('PlayerExplosion_')) console.log("Shuffling " + name)
+        else if (name == "PlayerExplosion_01-uhd") console.log("Shuffling death effects")
+
+        let sizes = {}
+        Object.keys(gameSheet).forEach(x => {
+            let obj = gameSheet[x]
+            obj.name = x
+            if (sheetNum == sheetNames.findIndex(y => y.startsWith('GJ_GameSheet02')) && forms.some(y => x.startsWith(y))) {
+                let form = forms.find(y => x.startsWith(y))
+                if (!sizes[form]) sizes[form] = [obj]
+                else sizes[form].push(obj)
             }
             else {
-                plist = plist.replace(`<key>${x}</key>`, `<key>###${newName}</key>`)
-                if (glowSheet[glow(x)]) {
-                    glowBackups.push(glow(x))
-                    glowPlist = glowPlist.replace(`<key>${glow(x)}</key>`, `<key>###${glow(newName)}</key>`)
-                }
+                /**@type {number}*/
+                let sizeDiff = assets.sheets[name] || 30
+                let size = obj.textureRect[1].map(x => Math.round(x / sizeDiff) * sizeDiff).join()
+                if (name.startsWith('PlayerExplosion')) size = "deatheffect"
+                if (!sizes[size]) sizes[size] = [obj]
+                else sizes[size].push(obj)
             }
         })
+
+        Object.keys(sizes).forEach(k => {
+            /**@type {{name: string}[]}*/
+            const objects = sizes[k]
+            if (objects.length == 1) return delete sizes[k]
+            const iconMode = forms.includes(k)
+            let oldNames = objects.map(x => x.name)
+            if (iconMode) oldNames = undupe(oldNames.map(x => x.replace(iconRegex, "$1")))
+            let newNames = shuffle(oldNames)
+            if (iconMode) {
+                let iconList = {}
+                oldNames.forEach((x, y) => iconList[x] = newNames[y])
+                newNames = iconList
+            }
+
+            oldNames.forEach((x, y) => {
+                let newName = newNames[iconMode ? x : y]
+                if (iconMode) {
+                    plist = plist.replace(new RegExp(`<key>${k}_${x}_`, "g"), `<key>###${k}_${newName}_`)
+                    glowPlist = glowPlist.replace(`<key>${k}_${x}_`, `<key>###${k}_${newName}_`)
+                }
+                else {
+                    plist = plist.replace(`<key>${x}</key>`, `<key>###${newName}</key>`)
+                    if (glowSheet[glow(x)]) {
+                        glowBackups.push(glow(x))
+                        glowPlist = glowPlist.replace(`<key>${glow(x)}</key>`, `<key>###${glow(newName)}</key>`)
+                    }
+                }
+            })
+        })
+        plist = plist.replace(/###/g, '')
+        fs.writeFileSync(wd + sheetNames[sheetNum] + '.plist', plist, 'utf8')
     })
-    plist = plist.replace(/###/g, "")
-    fs.writeFileSync('./pack/' + sheetNames[sheetNum] + '.plist', plist, 'utf8')
-})
 
-console.log("Shuffling misc textures")
-let specialGrounds = []
-assets.sprites.forEach(img => {
-    let spriteMatch = img.split("|")
-    let foundTextures = resources.filter(x => x.match(new RegExp(`^${spriteMatch[0].replace("#", "\\d+?")}-uhd\\.${spriteMatch[1] || "png"}`)))
+    console.log("Shuffling misc textures")
+    /**@type {string[]}*/
+    const specialGrounds = []
+    assets.sprites.forEach(img => {
+        const spriteMatch = img.split("|")
+        let foundTextures = resources.filter(x => x.match(new RegExp(`^${spriteMatch[0].replace("#", "\\d+?")}-uhd\\.${spriteMatch[1] || "png"}`)))
 
-    if (spriteMatch[2] == "*") specialGrounds = specialGrounds.concat(foundTextures.map(x => x.slice(0, 15)))
-    if (spriteMatch[2] == "g1") foundTextures = foundTextures.filter(x => !specialGrounds.some(y => x.startsWith(y)))
-    if (spriteMatch[2] == "g2") foundTextures = foundTextures.filter(x => specialGrounds.some(y => x.startsWith(y)))
+        if (spriteMatch[2] == "*") specialGrounds.push(...foundTextures.map(x => x.slice(0, 15))) // in-place `concat`
+        if (spriteMatch[2] == "g1") foundTextures = foundTextures.filter(x => !specialGrounds.some(y => x.startsWith(y)))
+        if (spriteMatch[2] == "g2") foundTextures = foundTextures.filter(x => specialGrounds.some(y => x.startsWith(y)))
 
-    let shuffledTextures = foundTextures.shuffle()
-    foundTextures.forEach((x, y) => fs.copyFileSync(`${gdPath}/${x}`, `./pack/${shuffledTextures[y]}`))
-})
+        let shuffledTextures = shuffle(foundTextures)
+        foundTextures.forEach((x, y) => fs.copyFileSync(`${gdPath}/${x}`, wd + shuffledTextures[y]))
+    })
 
-let emptyDict = glowPlist.match(/<dict>\s*<key>aliases<\/key>(.|\n)+?<\/dict>/)[0].replace(/{\d+,\d+}/g, "{0, 0}")
-let mappedBackups = glowBackups.reverse().map(x => `<key>${x}</key>${emptyDict}`).join("")
-glowPlist = fs.writeFileSync('./pack/GJ_GameSheetGlow-uhd.plist', glowPlist.replace(/###/g, "").replace(/<dict>\s*<key>frames<\/key>\s*<dict>/g, "$&" + mappedBackups), 'utf8')
-console.log("Randomization complete!")
+    let emptyDict = glowPlist.match(/<dict>\s*<key>aliases<\/key>(.|\n)+?<\/dict>/)[0].replace(/{\d+,\d+}/g, "{0, 0}")
+    let mappedBackups = glowBackups.reverse().map(x => `<key>${x}</key>${emptyDict}`).join('')
+    glowPlist = fs.writeFileSync(wd + 'GJ_GameSheetGlow-uhd.plist', glowPlist.replace(/###/g, "").replace(/<dict>\s*<key>frames<\/key>\s*<dict>/g, "$&" + mappedBackups), 'utf8')
+    console.log("Randomization complete!")
 
 }
 
-catch(e) { console.log(e); fs.writeFileSync('crash_log.txt', e.stack ? `Something went wrong! Send this error to Colon and he'll get around to fixing it at some point.\n\n${e.stack}` : e, 'utf8') }
+catch(e) {
+    console.error(e);
+    fs.writeFileSync(
+        'crash_log.txt',
+        e.stack ? `Something went wrong! Send this error to Colon and he'll get around to fixing it at some point.\n\n${e.stack}` : e,
+        'utf8'
+    )
+}