code: private float[] getNormal(float[] start, float[] end) {
  		float dx = start[0] - end[0];
  		float dy = start[1] - end[1];
  		float len = (float) Math.sqrt((dx*dx)+(dy*dy));
  		dx /= len;
  		dy /= len;
  		return new float[] {-dy,dx};
      }
docs: Get the normal of the line between two points
  
  @param start The start point
  @param end The end point
  @return The normal of the line between the two points