D2R Randomizer

A web-based mod generator for Diablo 2: Resurrected that shuffles all skill trees across every class to create unique, deterministic, and shareable playthroughs.

Live at d2rrandomizer.com

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What it does

Enter a seed number, choose optional mutations, and download a ready-to-install ZIP mod. Every skill from every class — Amazon, Sorceress, Necromancer, Paladin, Barbarian, Druid, Assassin, and Warlock — gets redistributed across all eight classes using a seeded PRNG. The same seed always produces the same result, so you can share a run with friends.

Skeleton Mastery shares a class with at least one of Raise Skeleton or Raise Skeletal Mage. Other summons still shuffle independently. Mastery's summon bonuses stay fixed instead of becoming random synergies.

The mod is offline-safe: it only touches skill tree files and does not require going online, so it will not flag your Battle.net account.

Mutations are optional difficulty modifiers (e.g. monsters move 50% faster, all skills cost double mana) that stack on top of the shuffle. Two mutations rotate each week as the weekly challenge.

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Tech stack

Layer	Technology
Frontend	Next.js 16 (App Router), React 19, TypeScript, Tailwind CSS 4
Backend	Next.js API routes (Node.js)
Image processing	sharp (sprite assembly)
ZIP packaging	archiver / adm-zip
Hosting	Single-instance Node on a Hostinger VPS (PM2 + nginx)

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Getting started locally

Prerequisites

• Node.js 20+
• npm

Setup

git clone https://github.com/<your-org>/d2r-skill-randomizer.git
cd d2r-skill-randomizer
npm install
npm run dev

Open http://localhost:3000.

The data/ directory is already included in the repository — it contains all the D2R game data TXT files the randomizer reads. You do not need a copy of the game to run the dev server or generate mods.

Building for production

npm run build
npm start

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Project structure

src/
  app/                      # Next.js pages and API routes
    api/randomize/          # POST — runs the full randomization pipeline
    api/preview/            # GET — returns skill tree preview JSON
    api/download/           # GET — returns the generated ZIP
    api/counter/            # GET — total generation count
    components/             # Shared UI components
    challenge/              # Weekly challenge page
    generate/               # Main generator page
    archive/                # Past weekly challenges
  lib/
    randomizer/             # Core randomization engine
      tree-randomizer.ts    # Assigns skill trees to classes
      skill-placer.ts       # Places skills within trees, respects pinned skills
      synergy-updater.ts    # Remaps synergy references to co-located skills
      prereq-assigner.ts    # Rebuilds prerequisite chains
      mutations/            # One file per mutation implementation
    mutations/
      registry.ts           # Mutation definitions + 26-week rotation schedule
    sprites/
      icon-assembler.ts     # Assembles per-class skill icon sprites
      tree-stitcher.ts      # Stitches full skill tree UI sprites
    data-loader.ts          # Parses TXT game data files into JS objects
    zip-builder.ts          # Packages mod files into the downloadable ZIP

data/
  txt/                      # D2R game data files (tab-separated)
  json/                     # Pre-parsed JSON cache (skills.json, skilldesc.json)
  skill_tree_grid.csv       # 6×3 grid layout for each class's three skill trees

public/
  mutations/                # Mutation card images (.webp)

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How the randomizer works

1. Seed — A Mulberry32 PRNG is initialized from the user's seed number. The same seed always produces the same output.

2. Tree assignment — Each class is assigned three skill trees drawn from the pool of 21 original trees (one from each of three index slots). Trees can be shared across classes.

3. Skill placement — ~45 skills are pinned to their original class (shapeshifting forms, dual-wield, etc.). The remaining ~195 skills are shuffled into the available slots, sorted by required level so low-level skills occupy the top rows.

4. Synergy remapping — Synergy formulas (skill('Name'.blvl)) are regex-replaced to reference skills that are actually present in the same tree.

5. Prerequisite rebuilding — Prerequisites are reassigned so that each skill in a row requires a skill from the row above it.

6. Sprite stitching — Skill icon sprites and skill tree UI sprites are assembled using sharp.

7. ZIP packaging — Modified TXT files and sprites are packaged as d2rr_export_[seed].zip, ready to drop into the D2R mods folder.

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Enemy shuffle (experimental)

The generator's Randomize monsters checkbox moves eligible ordinary monster families across acts and gives each replacement destination-appropriate levels and drops. The game's level scaling adjusts health, damage, defense, attack rating and XP using each donor's own stat multipliers. Separate limits handle resistances, status duration, critical hits and pack size. Starting-area Normal resistances are capped at 25%, so imported monsters cannot bring immunities. Nightmare and Hell retain each donor's original resistances and immunities without caps. It uses a separate seeded RNG, so enabling it does not change the skill trees. Bosses, scripted encounters and unsupported families keep their original spawns. The option defaults on for Season Beta Race and off for Turbo. Shared links preserve the selected setting; older links without enemyShuffle=1 keep it off. Mutation challenges enable it automatically starting with Challenge 15 (September 21, 2026); challenges 1–14 keep it off on replay.

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