// write as3 code here..
package {
    import flash.display.*;
    import flash.events.*;
    import flash.geom.*;
    
    public class BulletDemo extends Sprite {
        private var SPEED_FO:Number = 0.8;
        
        private var canvas_bd:BitmapData;
        private var ctf:ColorTransform;
        private var temp:Sprite;
        
        public function BulletDemo () {
            addEventListener( Event.ADDED_TO_STAGE, added );
        }
        
        private function added( e:Event ):void {
            if ( e.target == this ) {
                removeEventListener( e.type, arguments.callee );
                
                setup();   
            }    
        }
        
        private function setup():void {
            canvas_bd = new BitmapData( stage.stageWidth, stage.stageHeight, false, 0x000000 );
            addChild( new Bitmap( canvas_bd ) );
            
            ctf = new ColorTransform( SPEED_FO, SPEED_FO, SPEED_FO, 1.0 );
            temp = new Sprite();
            
            addEventListener( Event.ENTER_FRAME, update, false, 10 );
        }
        
        private function update( e:Event ):void {
            for ( var i:int = 0; i < 3; ++i ) {
                fire();
            }
            
            canvas_bd.unlock();
            canvas_bd.lock();
            canvas_bd.colorTransform( canvas_bd.rect, ctf );
        }
        
        private function fire():void {
            var x:Number = stage.stageWidth / 2;
            var y:Number = stage.stageHeight / 2;
            var v:Number = 3*Math.random();
            var a:Number = 0.1;
            var r:Number = 2*Math.PI * Math.random();
            
            var vx:Number = v * Math.cos( r );
            var vy:Number = v * Math.sin( r );
            var vr:Number = 0.03;
            
            var size:Number = 1 + 4*Math.random();
            var color:uint = 0xffffff * Math.random();
            
            var mtx:Matrix = new Matrix();
            
            var bullet:Sprite = new Sprite();
            bullet.graphics.beginFill( color );
            bullet.graphics.drawCircle( 0, 0, size );
            bullet.graphics.endFill();
            
            temp.addChild( bullet );
            
            bullet.addEventListener( Event.ENTER_FRAME, function( e:Event ):void {
                v += a;
                r += vr;
                vx = v * Math.cos( r );
                vy = v * Math.sin( r );
                x += vx;
                y += vy;
                mtx.tx = x;
                mtx.ty = y;
                
                canvas_bd.draw( bullet, mtx );
                
                if ( canvas_bd.rect.contains( x, y ) == false ) {
                    bullet.removeEventListener( e.type, arguments.callee );
                    bullet.graphics.clear();
                    temp.removeChild( bullet );
                    bullet = null;
                }
            }, false, 1 );
        }
    }
}

ぱーてぃくる