Part of the free-to-play-isation of Plants vs. Zombies 2 was locking certain levels off behind gates, requiring players to farm keys (ho hah!) or give in and buy them. That's gone with the latest ...
Devouring all those brains must have instilled some growing intelligence in PopCap's undead horde, as the free-to-play Plants Vs Zombies 2 has been updated with a number of clever fixes and additions.