function walk1():Void {
  A点からB点までの直線運動
}

function walk2():Void {
  B点からC点までの円運動
}

function walk3():Void {
  C点からD点までの直線運動
}

import mx.transitions.Tween;
import mx.transitions.easing.*;

var target:MovieClip = mc;

// AからBまで移動
function walking1(xTarget:Number, yTarget:Number):Void {
  var tw:Tween = new Tween(target, "_x", None.easeOut, target._x, xTarget, 5, true);
  var tw:Tween = new Tween(target, "_y", None.easeOut, target._y, yTarget, 5, true);
  tw.onMotionFinished = function():Void  {
    walking2();
  };
}
walking1(point_b._x, point_b._y);

// 円運動
function walking2():Void {
  var nTheat:Number = 60;
  var radius:Number = 60;
  var segment:Number = 0.02;
  var centerX:Number = center._x;
  var centerY:Number = center._y;
  var xpos:Number = radius*Math.cos(nTheat)+centerX;
  var ypos:Number = radius*Math.sin(nTheat)+centerY;
  this.onEnterFrame = function() {
    nTheat += segment;
    target._x = radius*Math.cos(nTheat)+centerX;
    target._y = radius*Math.sin(nTheat)+centerY;
    
    if (target.hitTest(point_c)) {
      delete this.onEnterFrame;
      walking3(point_d._x, point_d._y);
    }
  };
}

// CからDまで移動
function walking3(xTarget:Number, yTarget:Number):Void {
  var tw:Tween = new Tween(target, "_x", None.easeOut, target._x, xTarget, 3, true);
  var tw:Tween = new Tween(target, "_y", None.easeOut, target._y, yTarget, 3, true);
}