Introduction

J3 is an ahead-of-time compiled language for making games. It looks a little like Rust and a little like Zig, but it is smaller than either: there is no garbage collector, no borrow checker, and no escaping closures. What you get instead is plain data, explicit memory, and a compiler that turns your program into a native binary through LLVM.

module hello;

use j3.io.printLn;

fn main() {
    let name = "world";
    printLn(`Hello, {name}!`);
}

The compiler, j3c, is a single Rust binary with no dependencies. It carries the whole standard library inside it, so the version of the docs you read with j3c doc always matches the compiler you run.

What’s in the box

• The language: structs with methods, tagged-union enums, slices, arenas, generics with trait bounds, closures, and a ? operator for errors.
• The standard library: windows, input, audio, 2D and 3D rendering, an ECS, physics, UI components styled with CSS, networking, threads, and more, all written in J3.
• Tools: a formatter, a language server, a 3D scene editor, a script VM for hot-reloaded .j3s files, the j2 runtime for player mods, and packaging for zip, .deb, and Android.

How to read this book

Getting Started gets a program running. The Language part walks through J3 from values up to threads; each chapter builds on the last. The Compiler part covers j3c itself: commands, the j3.toml manifest, build modes, testing, and shipping.

When you need an exact function name, ask the compiler:

j3c doc                  # tasks and stdlib modules
j3c doc search <word>    # find a name in any module
j3c doc <module> --short # one module on one screen
j3c doc recipes          # complete, checked example programs