Hordes of the undead--check.
The formula for slaying zombies--more or less--varies a bit, but the end result is the same: Dispatch the Undead with prejudice--extreme or otherwise.
Zombie Shooter--though not the most imaginative name for a game designed to kill zombies--is impressive underneath the pedestrian moniker. Yes, it does tend to be a bit formulaic, as other games from Sigma Team seem to use the same engine to produce various derivations on the "shoot-to-kill" theme--whether they be zombies, aliens, or what have you--though I digress.
What is impressive is there is so much packed into the game: isometric-style viewing, multiple weapons, power-ups, challenging AI, detailed graphics, an engaging soundtrack and sound effects that are suitable without becoming overly annoying, and multiple situations for the player to test his or her expertise against the multitudes of types of zombies.
When played in a "quest"-style mode, the gameplay feels reminiscent of the Resident Evil-style of platform gaming, spread across a palette of challenging, multiple-level, console-type scenarios with a few puzzle twists to keep things interesting while eliminating the the zombies, rats, and whatever other hazards that may prove fatal to you as a zombie terminator.
Zombie Shooter is a pleasantly surprising game--for one that is free. Games of this genre, particularly with the large number of features that have been packed in, are almost always commercial, and cost accordingly. Sigma Team has lavished features found in other commercially-marketed, gaming titles, and have put them together in an user-adjustable package that players will find engaging in many repeatable, zombie-killing experiences.
Zombie Shooter can be found on the www.gametop.com website, free-of-charge, for Windows-based systems. The game, as tested, installs and plays well on Windows 7, and should be operational on Windows 8.x.
In the meantime, grab your ammo, make sure there are fresh batteries in your flashlight, and begin poking around in areas where the Undead shamble and swarm in the world of Zombie Shooter!