Game Objects

Game objects are the entity unit of KAPLAY. They are the actors of your game, the entities that move, interact, and make the game interesting.

Creating Game Objects

We create game objects with the add() function. It creates the object and attach it to the scene. It receives components and tags.

const dinosaur = add([
    // while components gives different behaviours to the game obj
    rect(32, 32), // draw a rect
    pos(80, 80), // set a position
    // tags classify the game object
    "dangerous",
    "big",
]);

We will see in deep components and tags in their respective guides.

Parents, childs and root

A game object can have child game objects. This will give to the children the possibility of follow parent’s position, rotation and scale.

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

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

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.

Game Object tree

That’s why the add() function is, in fact, a GameObjRaw.add() method.

Game Objects operations

How to create a game object

const bag = add([
    sprite("bag"),
]);

How to remove a game object

// you can use .destroy() method or the destroy() function
bag.destroy();
destroy(bag);

How to get all game objects

// get a list with all game objects
get("*");
// get a list of friends objects
get("friends");

How to add a child

// It adds a mini-bag to bag
const miniBag = bag.add([
    sprite("minibag"),
]);

const superMiniBag = bag.add([
    sprite("superminibag"),
    "favorite", // is the favorite
]);

How to remove a child

// We pass the game object reference
bag.remove(miniBag); // 18, independency

How to get childs

bag.get("*"); // all children
bag.get("favorite"); // [superMiniBag] - all children with tag favorite

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

The `make()` function

make() is used for creating a game object without adding it to the scene.

// Same syntax as add()
const bean = make([
    sprite("bean"),
    rotate(0),
]);

// No bean appears, but we can modify it
bean.angle = 270;

// Now make bean appears!
add(bean); // ohhi

Creating game object dynamically

One way for create a game object is create a function that returns a list of components:

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

const bullet1 = add(createBullet());

Another option is return an object with make(), and then add it.

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

    // we use a sprite if passed, if not a rect
    if (spr) {
        obj.use(sprite(spr));
    }
    else {
        obj.use(rect(6, 18));
    }

    return obj; // IMPORTANT: return the object reference
}

const bullet2 = add(createBullet("bullet")); // sprite
const bullet3 = add(createBullet()); // a rect

Basic Concepts

Components