What are some alternatives?
When comparing Fieldrunners and Towers of Oz, you can also consider the following products
Bloons TD - It's time, once again to achieve total Bloon popping satisfaction, this time in the form of...
Kingdom Rush - Epic game of tower defense available across multiple platforms.
Innotoria Tower Defense - Build, defend and annihilate legion of enemies in this new indie tower defense game
Bejeweled Blitz - Our games are sprinkled with a whirlwind of smile-inducing awesomeness and polished to a shiny sheen that keeps the world coming back again and again.
Robo Defense - Robo Defense is the ultimate portable tower defense experience.
TowerMadness - Tower Madness is an epic 3D tower defense game for iOS.