Given that there are now more tower defence games on mobile phones than there are stars in the night sky, one might assume that all opportunity for innovation within this crowded genre has vanished.

Thankfully, Asteroid Defense 2 proves that assumption wrong. While it maintains the core ethos of your typical tower defence game, the setting is subtly different.

Instead of valiantly protecting a patch of sodden earth, you’re propelled into planetary orbit to repel a shower of deadly meteors.

Granted, it’s not a complete paradigm shift, but the change does give Asteroid Defense 2 its own unique feel.

You start out with a command module, and must augment it with cannons, missile launchers, freeze guns, and shields. You also have to construct solar panels to ensure all of this ordnance has enough juice to function.

The final frontier

Your fearsome arsenal is pitted against a seemingly endless wave of rocks, some as small as footballs and others so large that they don’t even fit on the screen properly.

As you progress through Asteroid Defense 2’s excellent Campaign mode, you’ll find that the threats you face become ever more immense. Thankfully, as you play, you gain experience, which in turn boosts your level.

Passing certain level milestones unlocks the ability to upgrade your units, so you can boost the impact of your guns or make your solar panels even more effective at gathering energy.

Rock and roll

Asteroid Defense 2 does an excellent job of carefully drip-feeding you new units, and you can play for days before seeing all the game has to offer.

The Campaign mode will keep you busy for quite some time, and once you’ve completed it, you have the equally addictive Survival mode to face.

With excellent presentation and intuitive controls, Asteroid Defense 2 is impressive. The only drawback is that it doesn’t really offer a great deal more than its forerunner, which is available on the Android Market free of charge.

Cheap at half the price

This sequel may have better visuals and more content, but the relatively steep asking price (almost two quid at the time of writing) makes it a little harder to recommend completely - especially if you’ve already seen all the original had to offer.

However, if you’ve yet to experience the series, then we’d still advise that you skip the first game and lay down some cash for this version.

It’s a far better game in terms of execution, and it should do enough to convince you that there’s life in the tower defence genre yet.