Optimization Tips

Here’s some tips on optimizing performance / maintainability for KAPLAY games

Don’t use game objects everywhere

Game objects are great for managing game entities, but they have a cost. If you are only rendering a static image, or a simple shape, you can use onDraw with drawSprite or drawRect instead of creating a game object.

// create a game object
const player = k.add([k.sprite("bean"), k.pos(100, 200)]);

// draw a sprite directly
k.onDraw(() => {
    k.drawSprite({
        sprite: "bean",
        pos: k.vec2(100, 200),
    });
});

The same applies for other tasks like saving state or handling input. Sometimes it’s better to use global variables or functions instead of game objects for such tasks.

Cleanup One-off Objects

Sometimes there are some objects that gets created, leaves screen, and never seen again, like a bullet. These objects will keep being rendered / updated and be detrimental to performance if they get created a lot, it’s better to remove them when they leave screen.

offscreen() is a component that helps you define behavior when objects go off-screen.

k.add([
    k.sprite("bullet"),
    k.pos(player.pos),
    // the bullet move left forever
    k.move(LEFT, 600),
    // destroy the bullet when it's far out of view
    k.offscreen({ destroy: true }),
]);

Hide Off-Screen Objects

Sometimes you might be drawing a lot of objects that’s not on screen (e.g. if you have a big map and your camera only sees a small area), this is very unnecessary, use offscreen() component to define object’s behavior when they’re not on screen.

// planting flowers all over the map
for (let i = 0; i < 1000; i++) {
    k.add([
        k.sprite("flower"),
        k.pos(k.rand(-5000, 5000), k.rand(-5000, 5000)),
        // don't draw or update the flower when they're out of view
        k.offscreen({ hide: true, pause: true }),
    ]);
}

Use `await`

KAPLAY use a lot of Promise and Promise-like in time / event related stuff, use await on those to make code look nicer

async function example() {
    await k.wait(3);
    await k.tween(0, 100, 1, (x) => (mark.pos.x = x));
}

Avoid Global Namespace

By default KAPLAY uses a lot of common names like pos, sprite that occupies global namespace, it’s often better to use global: false to not export KAPLAY functions to window

const k = kaplay({
    global: false,
});

const pos = k.vec2(120, 200);

Use Game Object local timers

When programming timer / tween behavior for a specific game object, it’s better to attach timer() component to the game object and use that instead of global timer functions. This way the timer is tied to the life cycle of the game object, when then game object pauses or gets destroyed, the timer will not run.

// prefer
const player = k.add([
    k.sprite("bean"),
    k.pos(100, 200),
    k.timer(),
    k.state("idle"),
]);

// these timers will only run when player game object is not paused / destroyed
player.wait(2, () => {
    // ...
});

await player.tween(
    player.pos,
    k.mousePos(),
    0.5,
    (p) => (player.pos = p),
    k.easings.easeOutQuad,
);

// this will pause all the timer events
player.paused = true;

// this will stop all the timer events
player.destroy();

player.onStateEnter("attack", async () => {
    // ... state code
    // if we use global k.wait() here it'll create infinitely running state transitions even when player game object doesn't exist anymore
    await player.wait(2);
    player.enterState("idle");
});

player.onStateEnter("idle", async () => {
    // ... state code
    // if we use global k.wait() here it'll create infinitely running state transitions even when player game object doesn't exist anymore
    await player.wait(1);
    player.enterState("attack");
});

Use Game Object local input handlers

Similar to above, it’s often better to use local input handlers as opposed to global ones.

const gameScene = k.add([]);

const player = gameScene.add([
    k.sprite("bean"),
    k.pos(100, 200),
    k.area(),
    k.body(),
]);

// these
gameScene.onKeyPress("space", () => {
    player.jump();
});

// this will pause all the input events
gameScene.paused = true;

// this will stop all the input events
gameScene.destroy();

Compress Assets

Loading assets takes time, compress them when you can.

Compress .ttf or .otf to .woff2 (with google/woff2)
Compress .wav files to .ogg or .mp3