If you haven't ever played Tower Defense, then you've probably been doing actual work at work rather than frittering away your office hours playing web games. Curse you and your "work ethic."

Fortunately, Fieldrunners offers the perfect introduction to the distraction formerly known as Tower Defense. The object is to protect your base from an onslaught of enemies by placing weapons along a central pathway. As enemies waltz by, they get chewed up by your defenses. Touchscreen support makes it that much easier to plunk down defenses, of course.

You start with a blank playing field, a bit of cash, and limited time before some weak enemies start legging it across to the right hand side of the screen. Each time one these critters reaches your tower, you lose one of 20 lives.

So, you can place a few gatling towers in their way by tapping on the screen. These mow down enemies with ease, machine-gun style, earning you points that you can spend on more towers before the next wave. And the wave after that and so on, through 100 waves.

There are three other kinds of towers to build as well. Goo towers slow the enemies down, missile towers fire long-range rockets, and lightning towers offer the most powerful attack. Each can be upgraded twice for greater potency using money earned from battle. It's a basic set up to be sure, but there's a world of strategy to be explored within them.

For example, you quickly learn that the best way to build your towers is in a windy maze, forcing enemies to run the gauntlet of missiles and bullets down narrow corridors. Except you also need to carefully position goo and missile towers to ensure that you fend off the helicopters that occasionally form a wave and fly directly over the battlefield.

There's plenty to love about Fieldrunners. It looks great, for starters, with well-crafted cartoon visuals. Intuitive use of the touchscreen also helps. Icons lining the bottom of the screen allow you to simply drag towers into place on the map. A quick tap, should you have enough cash, upgrades the selected tower. You can even pinch in and out to zoom the viewpoint – all the better to admire those graphics.

There's a downside, though. Three difficulty levels provide replay value, as you try and move up to the next level after completing the game. It does need more variety, though, as there's only one playing field and four kinds of towers.

Simplicity is key, but this borders on being hollow. The lack of music and sound effects only serves to prove the point further. It looks great and has a dreadfully addictive quality, but it'll be even better once it has sound and a bit more variety in the levels.

Fieldrunners is still recommendable because it's enjoyable. Its shortcomings prevent it from being great, yet don't hold it back from delivering quick fun. Whether you're a Tower Defense expert or a newcomer (i.e. you still have a job), we thoroughly recommend it.