We knew Halo: Spartan Assault would be making its debut on Xbox One at some point this month, but today Major Nelson made the title's release date official. Starting December 24th, the new series spinoff will be available as a digital download for $15, with availability set to be worldwide. To make the deal sweeter for some, Microsoft is giving Windows 8 and Windows Phone 8 users who buy the game before December 15th a way to get the Xbox One version at a discounted rate of $5. Meanwhile, it appears Halo: Spartan Assault for Xbox 360 has been delayed, as Major Nelson revealed that it won't be available on said platform until sometime in January 2014. While you wait for it to arrive, check out the video after the break and get excited about your next adventure as a Spartan soldier.