// forked from _wonder's 複数のセグメントを連動させドラッグする：IK drag (5)
// forked from _wonder's 2つのセグメントを連動させドラッグする：IK drag (4)
// forked from _wonder's セグメントをドラッグする：IK drag (3)
// forked from _wonder's セグメントをマウスに向ける：IK(2)
// forked from _wonder's セグメントを描画：IK(1)
package {
    import flash.display.Sprite;
    import flash.events.Event;
    
    public class InverseKinematics extends Sprite {
        private var segments:Array;
        private var num:Number = 100;
            
        public function InverseKinematics() {
            init();
        }
        
        private function init():void {
                segments = new Array();
                
                //
                for( var i:uint = 0; i < num; i++ ){
                    var seg:Segment = new Segment( 4, 4, 0x000000 );
                    addChild( seg );
                    segments.push( seg );
                }

addEventListener(Event.ENTER_FRAME, onEnterFrame);
        }
        
        private function onEnterFrame( e:Event ):void {
            drag( segments[0], mouseX, mouseY );
            for( var i:uint = 1; i < num; i++ ){
                drag( segments[i], segments[i-1].x, segments[i-1].y );
            }
        }
        
        /* それぞれのセグメントの位置を決定する */
        private function drag(seg:Segment, posX:Number, posY:Number):void {
            var dx:Number = posX - seg.x;
            var dy:Number = posY - seg.y;
            var angle:Number = Math.atan2( dy, dx );
            seg.rotation = angle * 180 / Math.PI;
            
            //セグメントの位置をずらす
            var w:Number = seg.getPin().x - seg.x;
            var h:Number = seg.getPin().y - seg.y;
            seg.x = posX - w;
            seg.y = posY - h;
        }

}
}
import flash.display.Sprite;
import flash.geom.Point;

class Segment extends Sprite {
    private var color:uint;
    private var segmentWidth:Number;
    private var segmentHeight:Number;
    
    public var vx:Number = 0;
    public var vy:Number = 0;
    
    public function Segment(segmentWidth:Number,segmentHeight:Number,color:uint=0xffffff){
        this.segmentWidth = segmentWidth;
        this.segmentHeight = segmentHeight;
        this.color = color;
        init();
    }
    
    public function init():void {
        //セグメントの描画
        graphics.lineStyle( 0 );
        graphics.beginFill( color );
        graphics.drawRoundRect( -segmentHeight / 2, -segmentHeight / 2, segmentWidth+segmentHeight, segmentHeight, segmentHeight, segmentHeight );
        graphics.endFill();
    }
    
    public function getPin():Point {
        var angle:Number = rotation * Math.PI / 180;
        var xPos:Number = x + Math.cos( angle ) * segmentWidth;
        var yPos:Number = y + Math.sin( angle ) * segmentWidth;
        return new Point( xPos, yPos );
    }
}

紐のようなものをドラッグする：IK drag (6)