Rhai Scripting

Write game logic with Rhai — a lightweight, Rust-native scripting language.

Your first script

Create a file called scripts/player.rhai:

fn on_ready() {
    print("Player spawned!");
}

fn on_update() {
    let speed = 5.0;
    position_x += input_x * speed * delta;
    position_z += input_y * speed * delta;
}

Attach it to an entity in the Inspector. When you hit play, the entity moves with WASD.

Script properties

Expose variables to the Inspector so designers can tweak values without editing code:

fn props() {
    #{
        speed: #{ default: 5.0, min: 0.0, max: 100.0 },
        jump_force: #{ default: 10.0, min: 0.0, max: 50.0 },
        can_fly: #{ default: false }
    }
}

fn on_update() {
    position_x += input_x * speed * delta;
}

The speed, jump_force, and can_fly properties appear as editable fields in the Inspector with appropriate widgets (sliders, checkboxes).

Working with collisions

fn on_update() {
    if collisions_entered > 0 {
        print("Hit something!");
    }

    if active_collisions > 0 {
        print("Still touching");
    }
}

Entity hierarchy

fn on_ready() {
    print(self_entity_name);
    print("Children: " + children_count);
    print("Parent: " + parent_entity_id);
}

Rhai syntax basics

Rhai is similar to Rust and JavaScript:

// Variables
let x = 42;
let name = "hello";

// Functions
fn add(a, b) {
    a + b
}

// Control flow
if x > 10 {
    print("big");
} else {
    print("small");
}

// Loops
for i in 0..10 {
    print(i);
}

while x > 0 {
    x -= 1;
}