Getting Started

Installing

You need Rust (with Cargo) and clang on your PATH. Games that open a window also need SDL2, and 3D ones need OpenGL 3.3.

From the repository root:

cd j3c
cargo build --release

The binary is j3c/target/release/j3c. Put it on your PATH (the repo’s build.sh builds and installs it to $J3_BIN_DIR, else ~/.bin if that exists, else ~/.local/bin). Check it with:

j3c version

Your first project

j3c new mygame
cd mygame
j3c check
j3c run

j3c new writes a j3.toml manifest and src/main.j3. There are a few starting points:

Command	What you get
`j3c new mygame`	A console “hello” program
`j3c new mygame --app`	An SDL window with a game loop
`j3c new mygame --template fps`	A first-person 3D game with an editor scene
`j3c new mygame --template ui`	A window built from `.j3ui` components

The everyday loop

Command	Does
`j3c check`	Parses and type-checks. Fast; produces nothing.
`j3c run`	Compiles and runs the project.
`j3c build`	Writes the binary to `target/<name>`.
`j3c fmt --write`	Formats every `.j3` and `.j3s` file.

With no path these use ./j3.toml. You can also point them at a directory, a j3.toml, or a single .j3 file.

A window

Here is the shape of a small game loop using j3.game directly:

module game_loop;

use j3.game;
use j3.math.Vec2;

fn main() {
    let pos = Vec2 { x: 40, y: 40 };
    let running = true;

    while running {
        let dt = game.poll();        // pump input, get the frame time
        if game.quitRequested() || game.keyDown(game.Key.Escape) {
            running = false;
        }
        pos.x += 60 * dt;

        game.clear();
        game.drawRect(pos, Vec2 { x: 8, y: 8 });
        game.present();
    }
}

Bigger games usually use j3.app, a runner with startup, update, and draw stages. j3c doc recipes app2d prints a complete one.

Editor support

editors/vscode/ is a VS Code and Cursor extension: syntax highlighting, completion and diagnostics through j3c lsp, and Run/Build/Format commands. Set j3.j3cPath if j3c is not on your PATH.