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Guidebook Prerequisites

What every track needs before writing a line of mod code. Total: ~15 minutes.

1. Game + framework (all tracks)

Section titled “1. Game + framework (all tracks)”
  1. Install Data Center (Steam) and run it once.
  2. Install one loader: MelonLoader 0.7.2+ or BepInEx 6+.
  3. Install gregCore 1.2.3: extract the release ZIP matching your loader + OS into the game root, so gregCore.dll sits next to game_hooks.json and greg_hooks.json (Mods/ on MelonLoader, BepInEx/plugins/gregCore/ on BepInEx).
  4. Launch the game once. This creates UserData/gregCore/Mods/Lua/, UserData/gregCore/Mods/Scripts/, and UserData/gregCore/Mods/Lua/@shared/.

Verify: the loader log shows HWID SYSTEM ACTIVE and [DynamicPatcher] lines; in-game F1 opens the Mod Hub (GregModHub), F12 opens the Lua REPL, backquote (`) opens the gregCore console (help, mods, menus, keys, version). Details: Player Installation.

2. Per-track tools

Section titled “2. Per-track tools”
Track Tools Check
Lua Any text editor (VS Code recommended). No SDK, no build. You can create folders under UserData/gregCore/Mods/Lua/.
JS/TS Any text editor + tsc for TypeScript. No game build. You can create folders under UserData/gregCore/Mods/JS/. Types: templates/js/greg.d.ts.
C# .NET 6 SDK + local game + loader install. Copy MelonLoader/Il2CppAssemblies/ and MelonLoader/net6/ into the repo’s references/ once. dotnet build -c Release succeeds; python3 scripts/validate_version.py 1.2.3 exits 0.

Full C# environment (GameApi regeneration, coverage, mirror/CI): Developer Environment.

3. Folder layout you will use

Section titled “3. Folder layout you will use”
<Game root>/
├── Mods/gregCore.dll + game_hooks.json + greg_hooks.json   (MelonLoader)
├── UserData/gregCore/Mods/Lua/<modId>/main.lua + mod.json  (Lua mods)
├── UserData/gregCore/Mods/Lua/@shared/                     (Lua shared modules)
├── UserData/gregCore/Mods/Scripts/                         (general scripts)
├── UserData/gregCore/Mods/JS/<modId>/*.js                     (JS/TS mods — one folder per mod)
└── UserLibs/Js/*.js                                        (JS legacy — flat files, still loaded)

C# mods ship as compiled DLLs (built from templates/csharp/) and are deployed per scripts/Deploy-Release-ToDataCenter.ps1 conventions.

4. The three rules (all languages)

Section titled “4. The three rules (all languages)”
  1. Local-only. Data Center owns lobby, transport, and sessions. Mods never add networking (Developer Native Coop).
  2. Saves stay vanilla. Settings → config, state → save/sidecar, bulk files → sandbox. Never write vanilla save structures (Core Save Engine).
  3. Report honestly. Register what you are (manifest/registry), wire Hub openers/closers truthfully, gate missing dependencies instead of crashing (Developer Best Practices).

Checkpoint

Section titled “Checkpoint”