So earlier I was asking for help with something else related to this that has been somewhat resolved. My problem now is that the bubbles being created by the following code are appearing in the foreground no mater where I move the layer order.

Is there any sort of code that would put the bubbles in the background? I was thinking using .swapDepths could work somehow, but I can't seem to get it to work right if it is what I should use.

Thanks for your help.

PHP Code:
kNbrBalls = 20;
gravK = -0.0;            // gravity
dampK = 01;           // lower numbers make more air resistance
dampCollision = .99;     // energy retained in collisions

ballRadius = 15;
ballWidth = ballRadius*2;

SH = Stage.height;
SW = Stage.width;

MovieClip.prototype.handleCollisions = function()
{
    for (var i = mcs.length-1; i >= 1; --i) {
        var x1 = mcs[i]._x;
        var y1 = mcs[i]._y;
        for (j = i-1; j >= 0; --j) {
            var dx = mcs[j]._x - x1;
            var dy = mcs[j]._y - y1;
            var dist = Math.sqrt(dx*dx+dy*dy);
            if (dist < ballWidth) {
                // collide - trade energy (mag1,mag2), and travel in opposite direction of collision
                var mag1 = Math.sqrt(mcs[i].vx*mcs[i].vx+mcs[i].vy*mcs[i].vy);
                var mag2 = Math.sqrt(mcs[j].vx*mcs[j].vx+mcs[j].vy*mcs[j].vy);
                mcs[j].vx = (mag1*dx/dist)*dampCollision;
                mcs[j].vy = (mag1*dy/dist)*dampCollision;
                mcs[i].vx = -(mag2*dx/dist)*dampCollision;
                mcs[i].vy = -(mag2*dy/dist)*dampCollision;
            }
        }
    }
}



MovieClip.prototype.moveBall = function()
{
    // compute forces on ball
    if (!this.isDragging) {
        this.vx *= dampK;    // damping due to air resistance
        this.vy *= dampK;

        this.vy += gravK;    // gravity
        
        // bounce off floor and ceiling
        if (this._y+ballRadius + this.vy >= SH ||
            (this._y-ballRadius) + this.vy < 0)
        {
            this.vy *= -dampCollision;
        }
        // bounce off right and left walls
        if ((this._x-ballRadius) + this.vx <= 0 ||
             this._x+ballRadius + this.vx >= SW)
        {
            this.vx *= -dampCollision;
        }
        this._x += this.vx;
        this._y += this.vy;
    }
}

mcs = [];
for (var i = 0; i < kNbrBalls; ++i) {
  var mc = this.attachMovie("superball_mc", "mc"+i, 1+i);
  mcs[i] = mc;
  mc._x = ballRadius+random(Stage.width-ballWidth);
  mc._y = ballRadius+random(Stage.height-ballWidth);
  mc.vx = Math.random()*32-16;
  mc.vy = Math.random()*32-16;
  mc._width = ballRadius*2;
  mc._height = ballRadius*2;
  mc.onEnterFrame = mc.moveBall;
  mc.stop();
    choice = Math.round(Math.random()*4);

    switch (choice) {

    case 0 :

        mc.gotoAndPlay(1);

        break;

    case 1 :

        mc.gotoAndPlay(90);

        break;

    case 2 :

        mc.gotoAndPlay(180);

        break;

    case 3 :

        mc.gotoAndPlay(270);

        break;

    case 4 :

        mc.gotoAndPlay(360);

        break;
        }
}

_root.onEnterFrame = handleCollisions;