k.z() problem

game.js

import kaboom from "kaboom";

const k = kaboom({
    canvas: document.getElementById('canvas'),
})

k.loadSpriteAtlas("./assets/sprites/Tileset.png", {
    'traps': {
        x: 0,
        y: 0,
        width: 32,
        height: 32,
        sliceX: 1,
        sliceY: 1
    },
})

k.loadSpriteAtlas('./assets/sprites/Tileset.png', {
    'grass': {
        x: 0,
        y: 0,
        width: 32,
        height: 32,
        sliceX: 1,
        sliceY: 1,
    }
})

k.scene('main', () => {
    const map = [
        "===========================",
        "===========================",
        "==                       ==",
        "==                       ==",
        "==                       ==",
        "==  ==              ==   ==",
        "==  ==   ==LLLLL==  ==   ==",
        "==       =========       ==",
        "==       =========       ==",
        "==       ==     ==       ==",
        "==    =LL==     ==LL=    ==",
        "==    =====  @  =====    ==",
        "==           =           ==",
        "==                       ==",
        "==LLLLL==LLLLLLLLL==LLLLL==",
        "===========================",
        "===========================",
    ];

    // low fps
    k.addLevel(map, {
        width: 32,
        height: 32,
        "=": () => [
            k.sprite("grass"),
            k.z(11),
        ],
        "L": () => [
            k.sprite("traps"),
            k.z(11),
        ],
    })

    // high fps
    // k.addLevel(map, {
    //     width: 32,
    //     height: 32,
    //     "=": () => [
    //         k.sprite("grass"),
    //         k.z(10),
    //     ],
    //     "L": () => [
    //         k.sprite("traps"),
    //         k.z(9),
    //     ],
    // })
}
)

k.go('main')