Robo Boss

Spawns in the new waves as the fourth boss. It throws a power ball that deals damage to the towers it hits. The power ball deals 45 damage with a splash range of 6 studs.
There are two wave systems: the new wave system and the old wave system. In the new wave system, every 10 waves has a boss up until wave 190; after that, only zombies spawn. In the old wave system, bosses initially appear every 10 waves, but they spawn less frequently after wave 50. Wave 1000 contains the final boss.