The game has:
Single player
Co-op
Steam achievements
Trading cards
Full controller support
It is rated very positive.
Here is the info from Steam
About This Game
Yet Another Zombie Defense is all about defending yourself against hordes of undead attacking you every night. However, when you're the only survivor struggling against waves of enemies who are getting stronger and stronger, your end is inevitable. The only important question is how long can YOU survive?
The game is a top-down arcade zombie shooter with strategy elements. You're able to choose from variety of weapons to mount them onto auto turrets and set up defensive barricades to stay alive as long as you can. It's for gamers who like to put their skills to the test, find optimal strategy, and reach the highest spot on leaderboards! It also features online co-op mode, where you can blast zombies with up to three friends!
System Requirements
Minimum:
OS: Microsoft® Windows® XP/Vista/Win 7/Win 8
Processor: 2.0Ghz
Memory: 1 GB RAM
Graphics: Shader Model 3.0 compatible
DirectX: Version 9.0c
Hard Drive: 50 MB available space
Sound Card: DirectX 9.0c compatible
Good Game.
Definitely worth 49c. Got nothing to lose, just use your steam wallet funds from trading cards :)