code: function start () {
          var now = performance.now();
  
          if (typeof pausedAfter !== 'undefined') {
            startTime = now + pausedAfter;
          } else {
            startTime = now + delayMillis;
          }
  
          lastTime = startTime;
          pausedAfter = undefined;
  
          triggerEvent('start');
  
          startLoop(animationId, animationLoop);
  
          return self;
        }
docs: Start or resume animation