Boss Spawner FFC

//ZoriaRPG
//Spawn an npc that never returns after death.

const int NPC_MISC_BOSS_SPAWN_BIT_INDEX = 15; //The Misc[ index to use for this script.

ffc script spawn_boss {
    void run( int enem_id, int reg, int bit )
    //D0: THe ID of the enemy
    //D1: A Screen->D register. Should be unique for this screen. Valid range is 0 to 7.
    //D2: THe bit of the register. Should be unque per instance of this FFC on the screen.
    //  This is a bit value, in decimal, so use powers of two.
    //  The first instance of the ffc is 1, then 2, then 4, 8, 16.
    {
        int q; npc ; bool alive;
        if ( GetScreenDBit(reg,bit) )
        {
            this->Data = 0; Quit();
        }
        Waitframes(5);
        npc n = Screen->CreateNPC(enem_id);
        n->X = this->X; n->Y = this->Y; //Spawn the npc at the ffc coordinates.
        while(n->HP > 0)
        {
            //While this npc is alive, loop.
            Waitframe();
        }
        //this boss is dead.
        SetScreenDBit(reg,bit,true); //Set the bit so that it never respawns.
        this->Data = 0; Quit(); //Clean up the ffc and free it.
    }
}