Dark period of Zombie

Somewhere between mowing down zombie ninjas with a minigun, fighting a zombie T-rex,
and marveling at some sweet, 16-bit-looking graphics that made my heart smile,
it dawned on me that Dark period of Zombies is the most fun I've had on my phone in quite some time.
Never mind that this is another "zombie" game or that it's a Mini --
this game is great and I'm sure that Halfbrick could've gotten away with charging more than the game's $4.99 price tag.
The gist of "Age of Zombies" is simple: you're Barry Steakfries (a one-liner-dealin' dude who reminds you of every hero in every '80s action flick)
and you're getting teleported through time in an attempt to take out an army of zombies whipped up by a mad scientist.
You'll travel to ancient Egypt, the '30s, caveman days, and so on, but no matter where you go,
your only goal is to decimate the undead who have shown up and begun turning the gangsters and the mummies of the era into members of the zombie army.
To save the day, you'll move Barry around the screen with the D-pad or nub and shoot with the face buttons.
The screen is always looking down from the same perspective,
so shooting with X always mean shooting toward the bottom of the screen, Circle shoots right, and so on.
When you pick up grenades, mines, or the bazooka, these explosives are used by tapping the left shoulder button.
In essence, it's a twin-stick shooter without two sticks.
After playing so many twin-stick shooters on the phone,
the change to face buttons took me a few waves (you go through a few areas and then get to a time period's boss),
but once I got the hang of holding Triangle and Square to shoot in a northwest direction, everything was gravy.