---

name: Nethercore Development description: | Core development workflow for Nethercore games. Triggers on "nether build", "nether.toml", "asset handles", "determinism", "rollback rules", "WASM game".

Load references when:

• Full nether.toml examples -> references/nether-toml.md
• CLI command details -> references/cli-commands.md
• Determinism patterns -> references/determinism-rules.md version: 1.0.0

---

Nethercore Development

Overview

Nethercore games compile to WASM and run in the Nethercore player with rollback netcode. All consoles share the same WASM core, ensuring determinism across platforms.

Required Game Exports

Every game exports three functions:

Copy#[no_mangle] pub extern "C" fn init() { }   // Setup, asset loading
#[no_mangle] pub extern "C" fn update() { } // Deterministic logic
#[no_mangle] pub extern "C" fn render() { } // Drawing only

nether CLI

Game Manifest (nether.toml)

Copy[game]
id = "my-game"
title = "My Game"
author = "Your Name"
version = "1.0.0"

[build]
script = "cargo build --target wasm32-unknown-unknown --release"
wasm = "target/wasm32-unknown-unknown/release/my_game.wasm"

[[assets.textures]]
id = "player"
path = "assets/player.png"

Netcode (What You DON'T Do)

The Nethercore player handles all networking automatically:

• GGRS rollback synchronization
• State snapshots
• Input transmission
• Desync detection

Your only responsibility: Make update() deterministic. Never write: Networking code, rollback logic, state sync, or input transmission.

Determinism (Rollback Safety)

The update() function must be deterministic for rollback netcode. Given identical inputs, all clients must produce identical state.

Rules

1. All state in WASM memory - Use static variables (auto-snapshotted)
2. Use FFI random() functions - Never external randomness
3. Use tick_count() not system time - Frame-based logic only
4. render() is display-only - Never modify game state in render

Forbidden Patterns

Quick Test

Copynether run --sync-test --frames 1000

If this fails, you have non-deterministic code.

Project Structure

Copymy-game/
├── nether.toml          # Game manifest
├── src/
│   ├── lib.rs           # Entry point (init/update/render)
│   └── zx.rs            # FFI bindings (console-specific)
├── assets/
│   ├── textures/
│   ├── meshes/
│   └── audio/
└── Cargo.toml

Key principle: Keep entry files minimal (~50 lines). FFI bindings in separate module.