docs: function Follow (opts) {
      Follow.superclass.constructor.call(this, opts)
  
      this.followedNode = opts.target
  
      var s = require('../Director').Director.sharedDirector.winSize
      this.fullScreenSize = geo.ccp(s.width, s.height)
      this.halfScreenSize = geo.ccpMult(this.fullScreenSize, geo.ccp(0.5, 0.5))
  
      if (opts.worldBoundary !== undefined) {
          this.boundarySet = true
          this.leftBoundary = -((opts.worldBoundary.origin.x + opts.worldBoundary.size.width) - this.fullScreenSize.x)
          this.rightBoundary = -opts.worldBoundary.origin.x
          this.topBoundary = -opts.worldBoundary.origin.y
          this.bottomBoundary = -((opts.worldBoundary.origin.y+opts.worldBoundary.size.height) - this.fullScreenSize.y)
  
          if (this.rightBoundary < this.leftBoundary) {
              // screen width is larger than world's boundary width
              //set both in the middle of the world
              this.rightBoundary = this.leftBoundary = (this.leftBoundary + this.rightBoundary) / 2
          }
  
          if (this.topBoundary < this.bottomBoundary) {
              // screen width is larger than world's boundary width
              //set both in the middle of the world
              this.topBoundary = this.bottomBoundary = (this.topBoundary + this.bottomBoundary) / 2
          }
  
          if ((this.topBoundary == this.bottomBoundary) && (this.leftBoundary == this.rightBoundary)) {
              this.boundaryFullyCovered = true
          }
      }
  }