Start a game and hit pause then press c, a, l, l, d, a, d until you hear an orb weapon. It isn't done yet so don't un-pause. Keep entering the same code until the sound stops. Un-pause and you will be a fireant. Pause and proceed with c, a, l, l, d, a, d you will be a shield bug. When the shield wears off you will be invincible.