// js/game.js
function Game() {
  this.player = new Player({ name: 'ZuperAlex' });
  this.level = new Level({ nr: 1 });
}

Game.prototype.start = function () {
  ...
};

// js/app.js
var game;

function restartGame() {
  game = new Game;
  game.start();
}

restartGame();

var troll = {
    pos: [0, 0],
    sprite: new Sprite('img/troll.png', [0, 0], [200, 160]),
    hp: 5,
    maxHp: 5,
    delay: 500,
    resetHp: function(){
        this.hp = this.maxHp;
    },
    delay: function(){
        this.delay;
    },
    speed: 100
};

Troll.prototype.delay = function () {
  this.delay; //FIXME
};

// js/level.js
function Level(opts) {
  this.entities = [];
  this.nr          = opts.nr          || 1;
  this.trollCount  = opts.trollCount  || 1;
  this.spiderCount = opts.spiderCount || 5;
}

Level.prototype.addSpider = function () {
  this.entities.push(new Spider);
};

// js/game.js

function Game() {
  ...
  this.level = new Level({ nr: 1 });
  ...
}

Game.prototype.nextLevel = function () {
  var opts;
  var nextLevelNr = this.level.nr + 1;
  switch (nextLevelNr) {
    case 2:
      opts = { trollCount: 2, spiderCount: 5 };
      break;
    case 3:
      opts = { trollCount: 1, spiderCount: 10 };
      break;
    case 4:
      opts = { trollCount: 3, spiderCount: 5 };
      break;
    default:
      opts = { trollCount: 10, spiderCount: 20 };
      break;
  }
  opts.nr = nextLevelNr;
  this.level = new Level(opts);
};