code: func (r Rectangle) Intersect(s Rectangle) Rectangle {
  	if r.Min.X < s.Min.X {
  		r.Min.X = s.Min.X
  	}
  	if r.Min.Y < s.Min.Y {
  		r.Min.Y = s.Min.Y
  	}
  	if r.Max.X > s.Max.X {
  		r.Max.X = s.Max.X
  	}
  	if r.Max.Y > s.Max.Y {
  		r.Max.Y = s.Max.Y
  	}
  	if r.Min.X > r.Max.X || r.Min.Y > r.Max.Y {
  		return ZR
  	}
  	return r
  }
docs: // Intersect returns the largest rectangle contained by both r and s. If the
  // two rectangles do not overlap then the zero rectangle will be returned.