Another of the free online game genres that’s developed over recent times is that of Tower Defense.

I originally met the concept years ago with the seminal Real Time Strategy game Dune 2, from Westwood Studios when I discovered the strategy of defending my base from invading hordes by making walls out of rocket turrets.

Spinning forward from 1992 to 2007 and a flash game was released upon unsuspecting offices worldwide, Desktop Tower Defense. This started a trend of making free flash TD games, including the resource-capturing version Flash Element TD. There was clearly a niche to be carved out because the people behind this have formed the reasonably successful Casual Collective, with the flagship game, multiplayer Desktop TD. One of the winning gameplay elements is one of persistance, you get to have office leaderboards so you compare highscores between friends and refine maze design strategy.

Defense Grid: the Awakening is a 2009 version of the classic TD, but professionally developed and generally turned up to 11.

I discovered it after it got top marks in the January 2009 Indie game Round-up, andbeing distributed through Steam, the free demo was easy to get hold of.

If you haven’t played the genre before, Defense Grid’s first chapter walks you through the concepts and slowly ramps up the difficulty and complexity until you’ve got the hang of it. It was never easy, though, in the way that the free games can be once you’ve worked out a winning maze.

The graphics are 3D and well detailed, which does mean you need a reasonably recent computer to run it. The camera isn’t completely free form, limiting you to 3 isometric viewpoints, but it’s sufficient to let you get a good look at what you’ve constructed as it blows the alien robots to bits. The soundtrack is complete with a rich music layer and some full sound effects. It is fully voice acted with the computer sounding like it was educated at the BBC and it’s got a story overlain to give a bit more depth.

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I was surprised by this one. I thought that it wouldn’t add anything more to the free flash versions and was going to be a waste of time, but the professional presentation really added to the immersion and made it a good entertaining addition to the collection. Well worth the £13.