var scene, width, height, camera, cubeCamera, renderer, toruses, box;

init();
function init() {
  var boxGeometry, boxMaterial, light;

  scene = new THREE.Scene();
  width = window.innerWidth;
  height = window.innerHeight;
  camera = new THREE.PerspectiveCamera(45, width / height, 0.1, 1000);
  cubeCamera = new THREE.CubeCamera(1, 1000, 20);
  renderer = new THREE.WebGLRenderer();
  toruses = [];

  boxGeometry = new THREE.BoxGeometry(2, 2, 2);
  boxMaterial = new THREE.MeshBasicMaterial({ 
    envMap: cubeCamera.renderTarget,
    reflectivity: 0.8,
    color: 0xFFFFFF
  });
  box = new THREE.Mesh(boxGeometry, boxMaterial);
  box.position.set(0, 0, 0);
  scene.add(box);

  renderer.setSize(width, height);
  renderer.setClearColor(0x17293a);

  cubeCamera.position.set(0, 0, 0);
  scene.add(cubeCamera);
  camera.position.set(0, -50, 0);
  camera.lookAt(scene.position);

  generateToruses(200, 10);

  document.body.appendChild(renderer.domElement);

  drawFrame();
}

function generateToruses(num, step) {
  var torusGeometry, torusMaterial, torus,
      radius, colors;

  colors = ['#f1c40f', '#f39c12', '#e67e22', '#d35400', '#e74c3c', '#c0392b'];

  for (var i = -num; i < num; i += step) {
    radius = 4 + Math.random() * 8;
    torusGeometry = new THREE.TorusGeometry(radius, 1, 8, 30, Math.PI * 2);
    torusMaterial = new THREE.MeshBasicMaterial({color: colors[Math.floor(Math.random() * colors.length)]});
    torus = new THREE.Mesh(torusGeometry, torusMaterial);
    torus.position.set(0, 0, i);
    torus.rotation.set(-0.1 + Math.random() * 0.2, -0.3 + Math.random() * 0.6, 0);
    scene.add(torus);
    toruses.push(torus);
  }
}

function drawFrame() {
  var speed = 0.05;
  window.requestAnimationFrame(drawFrame);
  renderer.render(scene, camera);
  box.rotation.z += speed;
  box.rotation.y += speed;
  toruses.forEach(moveTorus);
  cubeCamera.visible = false;
  cubeCamera.updateCubeMap( renderer, scene );
  cubeCamera.visible = true;
}

function moveTorus(torus) {
  torus.position.z += 0.6;
  if (torus.position.z >= 200) torus.position.z = -200;
}