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s&box is a modern game engine built on Valve’s Source 2 and the latest .NET technology. It gives you a component-based scene system, built-in multiplayer networking, physics simulation, a Razor-powered UI framework, and a live-reload workflow — all in one package. Whether you’re downloading the editor from Steam or building the engine from source, this documentation covers everything you need to create games with s&box.

Installation

Get the s&box editor from Steam or build from source

Your first project

Create a scene, add components, and run your first game

Core concepts

Understand scenes, GameObjects, and the component model

API reference

Browse the full engine API surface

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Key capabilities

Component system

Attach reusable components to GameObjects to build any game mechanic

Multiplayer networking

Sync state and call RPCs across clients with a few attributes

Physics

Full rigidbody simulation, collision detection, and raycasting

UI framework

Build in-world and HUD interfaces with HTML/CSS panels

Hot reload

Edit C# code and see changes without restarting the engine

Action graphs

Wire up logic visually without writing code

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Getting started

1

Install s&box

Download the s&box editor from Steam or clone the repository and run Bootstrap.bat to build from source.
2

Create a project

Open the editor, create a new game project, and add your first scene.
3

Add a component

Create a C# class that inherits from Component, add it to a GameObject in the scene, and override OnUpdate to run game logic.
4

Hit Play

Press Play in the editor to run your game. Edit scripts and see changes applied live via hot reload.
If you want to contribute to the engine itself rather than build games with it, see the contributing guide.

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