Spawning and Controlling Multiple Enimies

programming
1

I want to be able to spawn little alien ships and have them fly down the screen, then I want to see if they either a) hit a laser b) hit my ship or c) go below the bottom of the screen.

For some reason I can’t get more then one ship spawned with this code. (P.S I’m using Flash MX 2004)
Here is my current code:

shipSpeed = 10;
laserSpeed = 20;
enemySpeed = 5;
enemySpeedx = 3;
i = 0;
n = 0;
score = 0;
shooting = false;
lives = 3;
_root.live = lives.toString();
_root.score = score.toString();
function shoot(laser){
 laser._y -= laserSpeed;
 
 if(laser._y < 0-laser._height){
  shooting = false;
  removeMovieClip(laser);
 }
}
function attack(enemy){
 enemy._y += enemySpeed;
 dir = caculateDir(findDir());
 if(dir == "left" and enemy._x - enemy._width*.5 > 0){
  enemy._x += enemySpeedx * -1;
 }
 if(dir=="left" and enemy._x-enemy._width *.5 <= 0){
  dir = "right";
  enemy._x += enemySpeedx;
 }
 if(dir == "right" and enemy._x + enemy._width*.5 < 350){
  enemy._x += enemySpeedx;
 }
 if(dir == "right" and enemy._x + enemy._width*.5 >= 350){
  enemy._x += enemySpeedx * -1;
 }
 if(enemy.hitTest(_root.ship)){
  enemy.play();
  lives--;
  _root.live = lives.toString();
 }
 if(enemy.hitTest(_root.laser)){
  iScore = int(_root.score)+5;
  _root.score = iScore.toString()
  removeMovieClip(laser);
  shooting = false;
  enemy.play();
 }
}
function spawnEnemy(){
 n = _root.getNextHighestDepth();
 trace(n);
 _root.attachMovie("enemy","enemy"+n,n);
 enemy = eval("_root.enemy"+n);
 trace(enemy);
 enemy._y = 0 - enemy._height;
 enemy._x = random(100)+enemy._width;
 enemy.onEnterFrame = function(){
  attack(enemy);
 }
}
 
ship.onEnterFrame = function(){
 if(Key.isDown(Key.LEFT) and ship._x > 0 + ship._width*.5){
  ship._x -= shipSpeed;
 }
 if(Key.isDown(Key.RIGHT) and ship._x + (ship._width*.5) < 350 ){
  ship._x += shipSpeed;
 }
 
 if(Key.isDown(Key.SPACE) and !shooting){
  shooting = true;
  i = _root.getNextHighestDepth();
  attachMovie("laser","laser"+i,i);
  laser = eval("laser"+i);
  laser._x = ship._x;
  laser._y = ship._y + laser._height;
 }
 laser.onEnterFrame=function(){
  shoot(laser);
 }
}
function findDir(){
 return random(1);
}
function caculateDir(dir){
 if(dir=0){
  return "left";
 }
 if(dir=1){
  return "right";
 }
 trace(dir+" is not an acceptable direction");
}
setInterval(spawnEnemy(),100);