old_contents: 'use strict';
  
  export default class Clock {
  	constructor() {
  		this.lastUpdate = window.performance.now();
  		this.deltaTime = 0;
  	}
  	update() {
  		var now = window.performance.now();
  		var delta = now - this.lastUpdate;
  		this.lastUpdate = now;
  		this.deltaTime = delta / 1000;
  		return delta;
  	}
  }
  
new_contents: 'use strict';
  
  export default class Clock {
  	constructor() {
  		this.lastUpdate = window.performance.now();
  		this.deltaTime = 0;
  	}
  	update() {
  		var now = window.performance.now();
  		var delta = now - this.lastUpdate;
  		this.lastUpdate = now;
  		this.deltaTime = delta / 1000;
  		return this.deltaTime;
  	}
  }
  
subject: Return the correct deltaTime in clock.update