phaserで横長の画像がアニメーションになる原理を知りたい

import Phaser from 'phaser';

class Entity extends Phaser.GameObjects.Sprite {
  constructor(scene, x, y, key, type) {
    super(scene, x, y, key);

    this.scene = scene;
    this.scene.add.existing(this);
    this.scene.physics.world.enableBody(this, 0);
    this.setData('type', type);
    this.setData('isDead', false);
  }

  explode(canDestroy) {
    if (!this.getData('isDead')) {
      this.setTexture('sprExplosion');
      this.setData('score', 0);
      this.play('sprExplosion');

      const sound = Phaser.Math.Between(0, this.scene.sfx.explosions.length - 1);
      this.scene.sfx.explosions[sound].play();

      if (this.shootTimer !== undefined) {
        if (this.shootTimer) {
          this.shootTimer.remove(false);
        }
      }

      this.setAngle(0);
      this.body.setVelocity(0, 0);

      this.on('animationcomplete', () => {
        if (canDestroy) {
          this.destroy();
        } else {
          this.setVisible(false);
        }
      }, this);

      this.setData('isDead', true);
    }
  }
}

export default Entity;

preload() {
    this.load.image('sprBg0', 'content/sprBg0.png');
    this.load.image('sprBg1', 'content/sprBg1.png');
    this.load.image('deathStar', 'content/deathStar.png');
    this.load.spritesheet('sprExplosion', 'content/sprExplosion.png', {
      frameWidth: 32,
      frameHeight: 32,
    });



    this.anims.create({
      key: 'sprExplosion',
      frames: this.anims.generateFrameNumbers('sprExplosion'),
      frameRate: 20,
      repeat: 0,
    });

    this.anims.create({
      key: 'sprPlayer',
      frames: this.anims.generateFrameNumbers('sprPlayer'),
      frameRate: 20,
      repeat: -1,
    });

    this.sfx = {
      explosions: [
        this.sound.add('sndExplode0', { volume: 0.1 }),
        this.sound.add('sndExplode1', { volume: 0.1 }),
      ],
      laser: this.sound.add('sndLaser', { volume: 0.1 }),
      r2d2Scream: this.sound.add('r2d2Scream', { volume: 0.1 }),
      useForce: this.sound.add('useForce', { volume: 0.3 }),
      vaderBreath: this.sound.add('vaderBreath', { volume: 0.1 }),
    };