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 tagged objects and iterate over them
get("friends").forEach((friend) => {
    // do something with each friend
});

How to add a child

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

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

// Now our original Bag is a grandfather...
const superMiniBag = bag.add([
    sprite("superminibag"),
    "favorite", // ...And 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 type definition.

Creating game object dynamically

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

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

const cake = add(makeCakeComps());

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

function addFriend(spr) {
    const posX = rand(0, width()); // Random position between 0 and width
    const posY = rand(0, height()); // Random position between 0 and height

    const obj = add([
        pos(posX, posY),
    ]);

    // If we pass a sprite, we use it
    if (spr) {
        obj.use(sprite(spr));
    }
    // If not, we use a circle
    else {
        obj.use(circle(16));
    }

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

const beanFriend = addFriend("bean"); // A Sprite
const circledFriend = addFriend(); // A Circled

Basic Concepts

Components