AZ Rockets doesn't look anything like Fire Balls 3D (it's far prettier and more abstract), but it's conceptually similar. It's another shooter that's all about timing rather than aiming and movement.
Your little rocket launcher moves along a twisting track, and you must time your taps to take out your targets, which happen to be letters that make up words. It's good fun, and a natural next step if you dug Voodoo's effort.
The Bug Butcher is kind of like a reinvention of Space Invaders, so it's mechanically a little bit more complex than Fire Balls 3D. But not by that much.
Enemies spawn in from above you, while you make your little gun slinger dodge left and right and blast them out of the sky. Think of this as your next target-shooting step after the simple delights found elsewhere.