duck

var waves : Wave[];
private var waveNum : int;
private var enemyNum : int;
private static var spawn : boolean;

function Start()
{
    waveNum = 0;
    enemyNum  = 0;
    spawn = false;
    var pos = transform.position;
    var rot = transform.rotation;

    for (var wave in waves) {
        for (var enemy in wave.enemies) {

            // wait until ok to spawn next enemy:
            while (!spawn) {
                yield;
            }
            Instantiate(wave[waveNum].enemies[enemyNum], pos, rot);
            spawn = false;
        }
    }
}