Phaser 3 this.physics is undefined following https://phaser.io/sandbox/edit/3

[Hello]

Hello I am following the sandbox code from https://phaser.io/sandbox/edit/3 with fair amount of refractoring but it says this.physics is undefined, any help appreciated
 

import Phaser from "phaser";

var player;
var platforms;
var cursors;
var jumpButton;

class PhaserProject extends Phaser.Scene{
  constructor() {
    super();
  }

  preload() {
    this.load.baseURL = "http://examples.phaser.io/assets/";
    this.load.crossOrigin = "anonymous";

    this.load.image("player", "sprites/phaser-dude.png");
    this.load.image("platform", "sprites/platform.png");
  }
  create() {
    player = this.add.sprite(100, 200, "player");

    this.physics.arcade.enable(player);

    player.body.collideWorldBounds = true;
    player.body.gravity.y = 500;

    platforms = this.add.physicsGroup();

    platforms.create(500, 150, "platform");
    platforms.create(-200, 300, "platform");
    platforms.create(400, 450, "platform");

    platforms.setAll("body.immovable", true);

    cursors = this.input.keyboard.createCursorKeys();
    jumpButton = this.input.keyboard.addKey(Phaser.Keyboard.SPACEBAR);
  }
  update() {
    this.physics.arcade.collide(player, platforms);

    player.body.velocity.x = 0;

    if (cursors.left.isDown) {
      player.body.velocity.x = -250;
    } else if (cursors.right.isDown) {
      player.body.velocity.x = 250;
    }

    if (
      jumpButton.isDown &&
      (player.body.onFloor() || player.body.touching.down)
    ) {
      player.body.velocity.y = -400;
    }
  }
  render() {}
}

const config = {
  type: Phaser.AUTO,
  default: 'impact',
  parent: "phaser-example",
  width: 800,
  height: 600,
  scene: PhaserProject,
};

const game = new Phaser.Game(config);