i am loving this game done all six of the levels on the main screen in a couple of hours, i really like games like this.
have you considered porting onto xna for the xbox 360 arcade, with a couple of bits added to make it multiplayer over live , i think you guys would have a hit.
also someone asked in another thread about planets, though i think it would make a person too powerfull you could have slightly raised areas indicating land masses instead and youcan take over a land mass. which then would help build a solar system- system for multiplayer.
