Ya MMM2 gets hard quickly but you just need to learn to upgrade to deal with it, and there are several options for doing so. Different waves require different approaches and technologies/upgrades, too. Once I found appropriate approaches, it was not too hard, but it was usually at least a bit challenging and fun and satisfying because of the momentum and fireworks.
I finished the Robokill free stuff. Is it worth 10 $ for two more episodes ? I like the game, but i absolutly dislike the spartanic weapon system. Blaster, Shotgun, Missile launcher, light, medium, heavy. I need more diversity ?