Game Objects

Game objects are the lower unit of KAPLAY. They are the actors of your game, the entities that move, interact, and make the game interesting. On this guide:

add() and make() functions to create game objects
GameObjRaw methods to manipulate game objects
Child game objects and the root game object
Object makers to create game objects with a specific set of components

Creating Game Objects

The first way to create game objects is the make() function: It assembles a game object from a list of components, but without attaching it to the scene. For that, we use the add() function.

const bullet = make([
    rect(6, 18),
    pos(80, 80),
]);

add(bullet);

In the other hand, we have the add() function. This function creates a game object and attaches it to the scene.

const player = add([
    rect(32, 32),
    pos(80, 80),
]);

Both operations create a game object with their respective components. Also, even an object without a component has some methods and properties, this interface is called the GameObjRaw.

Child Game Objects and the Root Game Object

A game object can have child game objects. This is useful to create complex game objects with multiple parts. We use the GameObjRaw.add() method to add a child game object.

const player = add([
    rect(32, 32),
    pos(80, 80),
]);

const head = player.add([
    circle(16),
    pos(0, -16),
]);

const gun = player.add([
    sprite("gun"),
    pos(0, 16),
]);

Something you should know is that every game object is a child of the root game object. The root game object is the game object that contains all the game objects in the scene. That’s why the add() function is, in fact, a GameObjRaw.add() method.

Game Object tree

Game Object operations

There’s a lot of operations that you can do with game objects. There’s a list of common operations:

destroy(obj) Destroy a game object
get(tag) Get a game object by its tag
GameObjRaw.destroy(): Destroy the game object itself
GameObjRaw.get(): Get a child game object by its tag, or all using obj.get("*")
GameObjRaw.children: Get an array with all children game objects
GameObjRaw.is(): Check if a game object has a tag/component

You can see the full list of operations in the GameObjRaw documentation.

Creating game object dynamically

There’s 2 used ways to create game objects dynamically. The first one is a function that returns a list of components. This is useful to create game objects on-demand.

function createBullet() {
    return [
        rect(6, 18),
        pos(80, 80),
        color(0.5, 0.5, 1),
    ];
}

const b1 = add(createBullet());

The second way is to use object makers. Object makers are factory functions that return a game object with make(). Is great for create game objects and manipulate them later, before attaching them to the scene.

function createBullet(spr: string) {
    const obj = make([
        pos(80, 80),
        color(0.5, 0.5, 1),
    ]);

    if (spr) {
        obj.use(sprite(spr));
    }
    else {
        obj.use(rect(6, 18));
    }

    return obj;
}

const b1 = add(createBullet("bullet"));
const b2 = add(createBullet());