Code snippet 7 - For multiplayer space invaders article

server.js

const envConfig = require("dotenv").config();
const express = require("express");
const Ably = require("ably");
const p2 = require("p2");
const app = express();
const ABLY_API_KEY = process.env.ABLY_API_KEY;

const CANVAS_HEIGHT = 750;
const CANVAS_WIDTH = 1400;
const SHIP_PLATFORM = 718;
const PLAYER_VERTICAL_INCREMENT = 20;
const PLAYER_VERTICAL_MOVEMENT_UPDATE_INTERVAL = 1000;
const PLAYER_SCORE_INCREMENT = 5;
const P2_WORLD_TIME_STEP = 1 / 16;
const MIN_PLAYERS_TO_START_GAME = 3;
const GAME_TICKER_MS = 100;

let peopleAccessingTheWebsite = 0;
let players = {};
let playerChannels = {};
let shipX = Math.floor((Math.random() * 1370 + 30) * 1000) / 1000;
let shipY = SHIP_PLATFORM;
let avatarColors = ["green", "cyan", "yellow"];
let avatarTypes = ["A", "B", "C"];
let gameOn = false;
let alivePlayers = 0;
let totalPlayers = 0;
let gameRoom;
let deadPlayerCh;
let gameTickerOn = false;
let bulletTimer = 0;
let shipBody;
let world;
let shipVelocityTimer = 0;
let killerBulletId = "";
let copyOfShipBody = {
  position: "",
  velocity: "",
};