src/animation/animation.js
/**
   * Perform a step of the animation
   * @param  {Number} delta      Time elasped since last frame
   * @param  {Drawable} drawable The drawable to operate on
   * @return {Boolean}           Return true to signal the end of the animation
   */
Perform a step of the animation
@param  {Number} delta      Time elasped since last frame
@param  {Drawable} drawable The drawable to operate on
@return {Boolean}           Return true to signal the end of the animation
Perform a step of the animation @param { Number } delta Time elasped since last frame @param { Drawable } drawable The drawable to operate on @return { Boolean } Return true to signal the end of the animation
step(delta, drawable) {
    if(!this.running) {
      return false;
    }
    this.elapsed += delta;
    if (this.elapsed > this.duration && !this.loop) {
      let t = this.timing(1);
      this.transform(t, drawable);
      this.stop();
      return true;
    }
    let t = this.timing((this.elapsed / this.duration) % 1);
    this.transform(t, drawable);
    return false;
  }
step ( delta , drawable ) { if ( ! this . running ) { return false ; } this . elapsed += delta ; if ( this . elapsed > this . duration && ! this . loop ) { let t = this . timing ( 1 ) ; this . transform ( t , drawable ) ; this . stop ( ) ; return true ; } let t = this . timing ( ( this . elapsed / this . duration ) % 1 ) ; this . transform ( t , drawable ) ; return false ; }
Perform a step of the animation
 @param  {Number} delta      Time elasped since last frame
 @param  {Drawable} drawable The drawable to operate on
 @return {Boolean}           Return true to signal the end of the animation
Perform a step of the animation @param { Number } delta Time elasped since last frame @param { Drawable } drawable The drawable to operate on @return { Boolean } Return true to signal the end of the animation
// if we're done with the animation