Halo: Spartan Assault has officially arrived for Windows Phone 8 and Windows 8 in each platform's respective app store. Available now for £4.99, the game has been created specifically with touchscreen devices in mind.

It has been released to coincide with Comic-Con 2013, currently taking part in San Diego, and offers a different kind of experience from the normal Halo fare. It is a top-down shooter, built entirely from scratch for mobile devices by 343 Industries and is based in the early days of the Spartan Ops programme. Halo fans will find plenty of back story and extra details that they might not have seen or heard before.

Read: Halo: Spartan Assault preview

Spartan Assault has 25 single-player missions and there is plenty of replay value as it includes Leaderboards to compare your scores and progress with friends'. There are weekly challenges, and 40 in-game achievements and medals to collect. You can also earn up to 50,000 experience points and an extra emblem for your Halo 4 Spartan.

In addition, purchase the app and you will unlock exclusive bonus content for the Halo 4: Champions Bundle or Halo 4: Bullseye Pack, both of which hit stores on 20 August.

More content is promised after launch.