Pixel Puzzles: UndeadZ is a jigsaw puzzle game with the distraction of fending off zombies. Instead of explaining what the heck a jigsaw puzzle is, I'm going to say what you need to know if you intend to play it right.
Play it with a big screen, and with a little more brightness than you find necessary. If your screen is smaller than 19", you're going to have a hard time with the size of the puzzle pieces in the later puzzles. Also, a lot of puzzles are dark, which becomes a pain in the butt when you are matching various colors of darkness.
You can turn off the distracting zombies when solving puzzles. The button to do so is to the right of the "Go" button.
The menu mini game gives you infinite grenades, and can be thrown with the RMB. This is how you get those pain in the butt survival achievements.
To use power ups, such as the extra wall or the trip mine, you need to click and drag with the LMB to place them. If you don't place them, you still pay for them, even though they don't get used.
Expect each puzzle to take a long time (30min to +120min), and there is no 'save and quit' function to pause in the middle of a puzzle. You can pause the game with the ESC key, but make sure to plan your games in advance.
I do recommend it to those diehard puzzle game fans (like myself), but this game definitely isn't for everyone. If the game could be paused and saved for later, I would say it would be a casual game. Play it when you have a lot of time on your hands.