Tower defence games are nothing new on the PC, or the Apple App Store for that matter. The primary difference between Fieldrunners and those that have come before is one significant detail: it costs money. Perhaps it's the global economic crisis speaking, or maybe we're just cheapskates, but as our iPod Touch downloaded Fieldrunners, we couldn't stop thinking "this had better be worth the money".
For the uninitiated, a tower defence game is where you control an omnipotent army general who places armaments across the field of battle to try and stop the enemy from running from their base to yours. As you progress through the levels, the number and strength of the enemy increases, but so does your income and ability to place more weapons on the field. The pace of the game speeds up and it becomes increasingly difficult to tell whether you have enough guns on the field to deal with the swarming hordes of infantry, tanks and helicopters.
The gameplay in Fieldrunners differs from the App Store's free variant, Tap Defense, but having an open field for the opposing army to move, rather than a predetermined path. This creates a whole other level of strategy as you try to manipulate the path the "baddies" run on by blocking their direction with your weapons. If you place your guns wisely, you can have the enemy running a maze of machine guns and missile launchers.
Graphically, you get what you pay for. Fieldrunners delivers a much slicker package all round, including sharper cartoon graphics and a better soundtrack. Fieldrunners also supports iPhone's now famous pinch and pull zoom gestures.