code: protected static int getDistanceEstimate (int ax, int ay, int bx, int by)
      {
          // we're doing all of our cost calculations based on geometric distance times ten
          int xsq = bx - ax;
          int ysq = by - ay;
          return (int) (ADJACENT_COST * Math.sqrt(xsq * xsq + ysq * ysq));
      }
docs: Return a heuristic estimate of the cost to get from <code>(ax, ay)</code> to
  <code>(bx, by)</code>.